GTPS Compression Ultimate Guide

Get That Pro Sound The Ultimate Guide to Compression First Edition Publication date: January 2013 Published by George Robinson Getthatprosound.com © Copyright George Robinson, All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, mechanical or electronic, including photocopying and recording, or by any information storage and retrieval system, without prior written permission from the publisher. While all attempts have been made to verify information provided in this publication, the Author does not assumes any responsibility for errors, omissions, or contrary interpretation of the subject matter herein. Of course, please let me know if you find any errors and I’ll correct them! The Purchaser or Reader of this publication assumes responsibility for the use of these materials and information. Neither the Author nor its dealers or distributors, will be held liable for any damages caused either directly or indirectly by the instructions contained in this book, or by the software or hardware products described herein.

Get That Pro Sound - The Ultimate Guide to Compression

Contents 1.

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Introduction......................................................................................... 4 Why Do We Need A Guide To Compression? What Is Compression, & Why Is It Useful?...................................... 5 Dynamic Range The Essentials: Set Up A Compressor In 30 Seconds.................... 7 4 Steps Anatomy of a Compressor Plugin.................................................... 8 Key Reverb Parameters.................................................................... 8 Other Common Parameters............................................................. 9 Compression Terminology.............................................................. 10 Compression Strategies: Assigning Compression In A Mix........ 12 Stage 1: Mix Balancing.................................................................... 12 Stage 2: Character Compression / Submix Compression........... 18 Stage 3: Stereo / Mix Buss Compression...................................... 21 Advanced Compression Techniques.............................................. 23 Parallel Compression...................................................................... 23 Sidechain Compression.................................................................. 25 Bonus Compression Pro Tips......................................................... 27 Conclusion......................................................................................... 32

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Introduction

Why Do We Need A Guide To Compression? Part of the problem with learning about compression and using compressors effectively is that it can be quite a challenge to even understand what compressors really do, or what it is we’re actually trying to achieve with them. Compression has to be one of the most confusing and elusive effects out there. People do ask about compression more than anything, because they find it the hardest concept to understand or hear. I was quite intimidated by the whole concept of compression for a long time, mainly because I couldn’t really hear exactly what difference it was making. But no more: Now the compressor is my best friend, and it can be yours too! Understanding what compressor parameters do in the abstract is not actually too difficult, given a proper explanation, but even then figuring out how best to deploy them in the context of a mix is tricky. How do you know whether or when to compress? How much compression is enough, or too much? What are the right attack and release times?

2 Key Things: The Importance Of Understanding Dynamics & Dynamic Range

Getting the results you want from compressors can often be the key to a tight, modern-sounding mix. Some producers will tell you that the importance of compression is often overstated, or that it’s not as important as EQ. But the thing about mastering compression is that you’re not really just learning how to operate a piece of equipment: you’re learning to listen to, understand and manipulate the internal dynamics of your tracks. Again, this is tricky: we’re talking about the relationships between sounds, and between the components of individual sounds – the envelope characteristics - as much as the discrete characteristics of those indidual sounds. It also means learning to listen in a different way than we’re used to: we’re used to evaluating sounds in terms of their frequency content. It’s easy for most people to say, “That sound is high frequency, that one is low.” But ask most people to evaluate a guitar part in terms of it’s attack or sustain, and those charcteristics help define the role of the instruments part in the context of a full mix, and it’s a different story. Compressors are your main tool for manipulating the dynamics of both individual hits and sounds, and the mix as a whole. Of course there are many factors that contribute to the dynamics of a sound, or a whole track: what sort of instrument created the sound, how it was played, and most importantly, the skill and sensitivity of the person giving the performance; but compression is our tool used to tame or accentuate the existing dynamics, or in some cases to introduce additional dynamics. One of the reasons people have a hard time understanding compression at first is that the differences in dynamics they introduce can be extremely subtle

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Get That Pro Sound - The Ultimate Guide to Compression – compression is as much about the cumulative effect of many individually compressed sounds being brought together, and the relationships between sounds with different dynamics, as it is an obvious process pasted over the whole track. This is why it’s important, once you grasp the basics, to consider an overall strategy for how you’re going to implement compression in a mix (much more on this later). Part of the reason it’s difficult at first is that you’re listening for changes in the transients/dynamics rather than the frequency content. We can all tell the difference a high frequency sound and a low one, but to the untrained ear it can be a bit more tricky figuring out what’s happening to the dynamics of sounds through a compressor, and more pertinently what settings are going to sound the best in the context of a complete mix. But once you get how the internal dynamics and dynamic range of individual sounds and complete mixes can be controlled and shaped, not only will you feel like a sonic wizard, you’ll be well on your way to becoming a Pro Sound master. Remember: experiment, listen, and you’ll get it at some point. It’s easy when you know what to listen for.

What is Compression, & Why Is It Useful? Your Personal Level Riding Assistant

At it’s most basic, a compressor is basically an automated level fader – when the audio is loud it gets turned down and when it’s soft it gets turned up. Imagine you’ve got your very own studio lackey whose job it is to ride the fader on each track, incredibly quickly and accurately. It will monitor all the incoming signals and then act like it is pulling down the fader the instant that high volume peak occurs. In a more technical explanation, what the compressor is actually doing is reading the incoming signals, and then according to the compression ratio that you set, it knocks the hot signal down by that ratio. This allows you to keep the level down to one that is manageable and recordable, without the wild peaks. [and vice versa: automatically bringing up very low level signals].

Why Is Compression Useful? Introducing Dynamic Range

Compressors were originally invented (apparently for location recording for the first ‘talkies’ in Hollywood) to reduce the dynamic range (see the box on the left for an explanation of dynamic range) of a recording, making it less likely to distort at the recording stage, and easier to balance with the other parts at the mix stage. Think of a very dynamic part, such as a vocal line: throughout the track you might want to hear everything from intakes of breath before each line to the full-on chorus at the climax of the song. There are going to be loud sections and relatively quite sections within the same performance; and when it comes to the mix, you would either have to turn the whole thing up loud enough to hear the quietest notes and breathes, making

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Get That Pro Sound - The Ultimate Guide to Compression the choruses ridiculously overbearing, or vice versa: turn everything down, and lose completely all the details and nuances of the performance. Essentially, no static level gives a good balance because the difference between the highest and lowest signal levels – the dynamic range – is too large. Compressors remedy this problem by reducing a sound’s dynamic range. It will reduce the level differences between the loudest and quietest parts, making it easier to find a static fader setting that works. The compressor does this by turning down – ‘compressing’ – the louder parts so that they match the quieter parts more closely — and all it needs from you is an indication of which signals you think are too loud. That’s the original, technical use of compression. However, things got a lot more interesting when people realised that the ‘side-effects’ of heavier compression – smoother sounds, more sustain, fatter notes and punchier drums – could actually be very pleasant. Compressors could be used to manipulate the dynamics of sounds creatively: not just keeping levels within certain technical limits, but changing the character of the sound, accentuating or diminishing certain aspects of a single part or instrument.

Dynamic Range: One-Paragraph Primer

The lowest level in the dynamic range is the noise floor. You’ll generally only find tape hiss and electrical hum here. Next up is the nominal level, which is the best level for recording your incoming signal in order to minimize distortion and overcome the noise floor. The difference between the noise floor and the nominal level is called the signal-to-noise ratio. Finally there is the highest level in the total dynamic range, the maximum level: any level beyond this will not be reproduced properly and will distort (0dB in your DAW). The difference between the nominal level and the maximum level is referred to as the headroom. You’ll want to make sure that even stray loud peaks stay within your available headroom. So, when we talk about total dynamic range, we’re talking about the difference between the noise floor and the maximum level. So if compressors reduce dynamic range, are they making loud sounds quieter or quiet sounds louder? The answer is they can do either. The mechanism of compression means that loud sounds are reduced – ‘compressed’ – in level, but compressors generally also have an output level control to compensate for the loss in gain and bring the overall level back up. Stay with me, because here’s a key aspect of compression: If you apply enough make-up gain to bring the peak levels back to where they were before compression, the quieter signals will be louder than before; so you can think of compression as both a way to make loud sounds quieter and to make quiet sounds louder.

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Get That Pro Sound - The Ultimate Guide to Compression As quieter parts of sounds can, in effect, be increased in level relative to the loudest peaks, compression ultimately has the effect of boosting the average signal level. This, in turn, means that the average energy level is higher: which generally results in a more powerful or punchy sound, even though the peak level is unchanged.

The Downside: The Compression Tradeoff

You may be thinking, if compression is so good, why not use loads of it, on everything? What happens when you over-use compression? Take a typical rhythm guitar part. You may want to have as much sustain to the notes as possible, that wasn’t in the original recording, and so you apply some really heavy compression to bring up the level of the quiet tails of each note and make them sustain for ages. But in the process, you have eliminated your original playing dynamics, so while you have all the sustain you wanted, you’ve lost the nuances in your accented notes and phrases. The attack of an instrument is a very important factor in the instrument’s sound, and heavy compression can take the ‘life’ out of an instrument or performance. Having said that, there are ways around this limitation, which we’ll discuss later when we look at Parallel Compression.

The Essentials: Set Up A Compressor In 30 Seconds

Start with a low threshold of around -20 or -25 dB – this will then enable you to clearly hear what all the other controls and adjustments are doing to your sound. Once you have those optimally set, you can bring the threshold back up to a more useable level, adjusting to taste. (Remember to stop, use your ears and close your eyes at every step of the process. You can tweak the knob without looking at it. It’s quite a different experience, and you’ll get better results making judgements by ear.)

1. First, insert a compressor plugin on an audio track. Set the Ratio to a typical starting value of

2:1 or 3:1, and immediately bring the Threshold down quite low to around -20dB to -24dB – this will then enable you to hear very clearly what all the other controls and adjustments you’re going to make are actually doing to your sound. Once you have those optimally set, you can bring the threshold back up to a more useable level, adjusting to taste.

2. Play back your material on the track where your compressor is inserted. Try sweeping the Attack control from fastest to slowest, and listen to the difference in sound. Then do the same with the Release control. Leave the Attack and Release at settings that feel appropriate to the material you’re playing back. 3. Go back and tweak the Ratio a little bit to understand what it does. Essentially, the Ratio

compresses peaks above the threshold more. With this method, you’ll often be able to find a combination of settings that just seems to work intuitively with your sounds, particularly drums: this is what’s known as tuning the compressor to the sound you want to achieve.

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4. The amount of compression or Gain Reduction is usually indicated on a meter, and you can use this as a guide to, for example, ‘apply between 3dB and 5dB of gain reduction’ on the loudest peaks/notes.

Anatomy Of A Compressor Plugin Key Compressor Parameters

Every compressor will have these essential controls:

Threshold

This as the decibel level at which the compressor will start working. You can think of it as a line that is lowered onto your signal: the lower the threshold level, the more the incoming signal will be compressed. This is because more of the noise peak is now above the threshold level, so there is more to squash. Also keep in mind that if your incoming signal never reaches the threshold level, (or the threshold is set too high), none of the signal will actually be compressed.

Ratio

This refers to how much the signal above the threshold is reduced, relative to it’s original level. For example, if you set the ratio to 3:1, for every 3dB your incoming signal goes above the threshold, the compressor will allow only 1dB to pass. The level still goes over the threshold, but assuming that you set the threshold low enough and used an appropriate ratio, the peak won’t have reached the maximum level and distort.

Attack

This refers to how fast, in milliseconds, the compressor acts on the peaks once they pass the threshold. The attack setting becomes critical when dealing with instruments that have a pronounced attack of their own, such as bass guitar or most drums, because if you’re trying to control the peak levels, you want to make sure that the compressor is responding fast enough to the incoming signal, with a very fast attack setting. At othe rtimes you may want to let the attack portion of a note through and only process the later body of the sound: in this instance, setting a slower attack time will be the way to go.

Release

This refers to how fast the compressor ‘lets go’ of the incoming signal once it has gone back below the threshold level, where the signal doesn’t need to be compressed anymore. The release time is generally longer than the attack time. You can set up a fast/short release time and cut off the signal processing quickly, or set it slower, which would result in greater sustain on each note or hit. Many guitar players use compression like this, for extra sustain.

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Make-Up Gain / Output

As we mentioned already, squashing a signals dynamic range will generally change its apparent overall level. So the Output Gain (also called Make-up Gain, or simply Gain or Make-up), simply allows you to reinstate the compressed signal back to a useful, nominal level in the mix. Something to be aware of here is that by raising your signal back to the nominal level, you are also bringing up the level of the noise floor by the same amount. If you find yourself using a very high Make-up Gain setting, you might want to try increasing the level of the signal going into the compressor to begin with instead.

Other Common Parameters

Not every compressor model has these options, but many do:

Knee

A feature common to many compressors is the option to compress with ‘hard knee’ or ‘soft knee’. With a hard knee setting, the signal is compressed the moment it goes above the threshold to the full extent of the ratio that is set. With a soft knee setting, the compression is applied more gradually – literally more softly – making the effect of the compression less abrupt and audible; which also means more overall compression can be applied. Soft knee compression is typically suitable for vocals and whole mixes; hard knee compression is usually right for bass and drums. You can think of choosing the knee setting of a compressor as similar to setting the attack knob – it adjusts how ‘tough’ the compressor appears to be on your signal.

Sidechain / Key

Some compressors are able to ‘listen’ to another signal and apply compression, based on that ‘sidechained’ source signal, to the process sound. The extra signal is also sometimes referred to as the ‘Key’ or ‘Key Input’. There are subtle, technical uses for sidechain compression, but it’s also very common as a creative effect in dance and electronic music. Here it can usually be heard where the kick drum appears to punch holes in the bass, synth and pad parts every time it hits, creating an extremely dynamic sucking or whooshing sound (see Breathing and Pumping below). Sidechain compression as a specific technique is covered in a later chapter.

Stereo Link

On dual-channel compressors, the Stereo Link switch usually sums the two inputs together, controlling them as if they were a single source. This is useful when you’re compressing stereo signals, where you want to be sure that both channels are being compressed by exactly the same amount, which would not otherwise necessarily be the case if you have different sounds panned to different sides of the stereo field. For example, if you have a loud sound panned hard to the left, the left channel level will be pulled back by the compressor, which in turn will make the mix appear to swing towards the unprocessed (because there’s no sound) right channel.

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Switchable Peak/RMS modes

Compressors are designed to respond pretty much like the human ear, which means that short duration sounds aren’t perceived as being as loud as longer sounds of exactly the same level. This is called an RMS response (an abbreviation for ‘Root Mean Square’), a mathematical means of determining average signal levels. The implications of using a compressor with an RMS control law are that the compression will sound natural, but short duration, high amplitude sounds may pass through at a higher level than you expect. One solution when feeding digital systems that can’t tolerate overload is to use a fast acting peak limiter after the compressor. Some compressors allow you to switch how they respond to incoming signals. In RMS (which stands for ‘Root Mean Square’) mode, the compressor responds much like the human ear, in the sense that short duration sounds aren’t perceived as being as loud as longer sounds of exactly the same level. This results in natural-sounding compression, but short, loud sounds may slip through without being processed the way you would expect. This is where Peak mode comes in. Here, the gain control responds more accurately to brief signal peaks than in the RMS ‘averaging’ mode. This ensures peaks are more accurately controlled, but the potential downside is that it can also squash everything more harshly whenever a loud, short transient sound occurs. Because of this, Peak compression is generally reserved for tasks like treating individual drum and percussion sounds, where the transient peaks are a larger part of the overall sound than with other instruments.

Compression Terminology Breathing And Pumping

When you set very short attack and/or release times, these can require the compressor to make very fast changes in the gain. When the effect created by thiese sudden/extreme changes is audible, whether by accident or by design, it’s referred to as ‘breathing’ or ‘pumping’.

Linear vs. Non-Linear

In theory, the amount of gain reduction that a compressor applies as the input goes above the threshold should be reasonably linear: so no matter by how much the input exceeds the threshold, the output level increase will always be the fraction of that amount determined by the ratio setting. However, most compressor models are not perfectly linear. Because of the inner workings of valve-type technology, it’s not uncommon for the amount of gain reduction to reduce at higher signal levels: effectively lowering the ratio of compression at those higher levels. This isn’t generally regarded as a fault, but a feature of many of the most celebrated compressors, that contributes to a specific, ‘musical’ character of their own.

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Transparent vs. Character Compression

Linked to the differences between linear and non-linear compression, these terms refer to how ‘invisibly’, or otherwise, different compressors process material. Sometimes you’ll want to compress a part without the audible side affects that give away that it has indeed been processed; you want the compressor to work ‘transparently’. Conversely, you may very well want to imbue your sounds with nice tube warmth (subtle distortion inherent in most analogue circuitry), or introduce the audible dynamic effects of heavy compression; in this case, you’ll want to reach for a non-pristine, non-linear ‘character’ compressor that will favourably colour your material.

Three Classic Compressors: Three Compression Control Paradigms There are three favourite hardware compressor models that between them illustrate the three most common control layouts found in any compressor, whether hardware or plugin. The differences are essentially how you control the amount of compression that is applied. If you want to really get under the skin of your favourite plugin compressors, it can be useful to figure out which of the classic types they are most similar to – this will give you some good ideas for what type of material your plugins might be best suited to.

Teletronix LA2A

Turn up the peak-reduction knob to increase the amount of compression.

SSL Buss Compressor

You get more compression as you bring the threshold down. The Waves Renaissance Compressor plugin uses this method.

UREI 1176

The input gain control pushes the signal up against a fixed compression threshold to increase the amount of compression.

One-Knob Compressors

There are also a few ‘one-knob’ compressor designs with only a single Compression control. These generally have some kind of automatic Make-up Gain function working behind the scenes, keeping the subjective level of the audio consistent no matter how much compression you’ve dialled in. Clearly these compressors are fast and simple to control, making them useful for dramatic, character effects. Just be aware that it’s especially easy to overdo the amount of compression applied with this type!

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Compression Strategies So now we know what compressors are designed to do in principle, and how the different controls work together to enable us to achieve that. But how do we implement compression smartly in the real-world context of a mix, and as a creative tool? As we’ve already discussed, effective compression is far more about creating a cumulative effect built up through a mix than it is pasting on heavy compression at the end, all in one go. It’s time to formulate a strategy, so that we can build the most effective and flexible overall effect.

A Note On Compression While Recording

With recording it’s generally best to keep everything as ‘dry’ of effects and processing as possible, because if you track anything with additional processing included in the recording, you won’t be able to change it later if you want to. However, in some instances processing an incoming signal for recording is smart. If you’re recording a vocal, for example, or any instrument with a high dynamic range, it will be quite easy to overload the recording device, introducing unwanted distortion. This is a typical case where you’ll want to apply some light, transparent compression just to tame any wild peaks and make sure that you’re going to be working with a clean recording.

Stage 1: Using Compression To Fix Mix Balance Issues

Which Parts Do I Need To Compress, and at What Point in the Signal Chain? So, assuming you’ve got your arrangement of cleanly recorded tracks up in your DAW, it’s time to start with our mix compression strategy. Every mix will be different, but pretty much everything in a modern production will sound better with at least a little compression, from kick drums to flutes. However, some instruments are typically more likely to need dynamic-range control than others – vocals, bass and drums are the usual key places to start. Whilst it’s of limited use to offer totally prescriptive settings for these, here are some good jumping-off points for common instruments:

Which Parts Do I Need To Compress? Vocals

Vocals are the obvious place to start with applying compression. Although they naturally have a very wide dynamic range, they’re the main carrier of the vital melody and lyrics in most songs, and so you actually want to maintain a relatively small dynamic range. Even in natural-sounding acoustic mixes, some control of vocal levels will usually be required. This

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could technically also be achieved though fader automation, but it’s typically much more effective to use compression. 1. We’ll start by catching and controlling the loudest peaks in the performance. The ratio to start at will vary from singer to singer: some voices are very strong and loud, others will be quieter, with a smaller dynamic range. Try starting with a 2:1 ratio on sung material (but try as high as 6:1 for voiceovers or spoken word), use a soft-knee setting, a fast attack (e.g. 0.09ms) and medium to slow release (100ms). 2. With the vocal playing back, lower the threshold until the compressor is working on the signal peaks – you’ll know you’re in the right ballpark when the meter is displaying between 3dB and 8dB of gain reduction on the loudest notes only. 3. Bring the Output or Make-up Gain control up to compensate for the level drop.

Bass

Compression is key for bass parts of all types – synth, electric bass guitar, acoustic – as here it will help you get a really consistent, solid foundation on which to build the rest of your track. Bass guitars in particular can have quite a wide natural dynamic range, but even where the dynamics are already quite restricted compression is advised because of the importance of controlling the levels of low mix frequencies. Start with a 4:1 ratio, fast attack and fast-to-medium release. It can work to bring the threshold down lower than you would simply to catch stray peaks: bass benefits from, and can handle, relatively strong initial compression. Generally use a hard-knee compressor/setting if you have the choice, as having strong control of the attack of a bass sound is key to shaping it’s overall sound.

Drums

Drums are usually compressed due to their hard attack/transients, and can be transformed by compression in a mix – one thing to remember is that pretty much anything you do will be an effect. As such, it’s even more tricky to advise starting settings! But here are some tips and things to consider: It can be a good idea to set any drum compressor to a medium-slow attack, which will allow more of the initial transient through, giving the hits more snap, stick or beater so they retain teir ability to punch through a mix. You can also try aiming to set the release to a speed where it can return to zero between beats, so the compressor is working with the groove, not against it. When compressing a live drum performance, the best threshold and ratio settings will depend on the consistency of the drummer: with a less consistent drum track, try using a lower ratio to maintain as even a sound as possible.

Kick, Snare And Toms

If nothing else, at least compress the snare, because this drum will have particularly loud

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transient peaks on each hit. With a soft knee setting, start with a 4:1 ratio, fast attack and a slightly slower release. Then, playing back, lower the threshold to grab just the loudest peaks, for 1-2dB of gain reduction. To adjust the snare sound to best fit your track, try sweeping the attack faster or slower to find a sweet spot, and bringing the threshold higher to taste e.g. an R&B ‘snap’ or more of a pop ‘slap’.

Cymbals

Start with a 2:1-3:1 ratio, fast attack – and a slow release to preserve the natural decay.

Overhead Mics

For some life-giving sizzle, try limiting (compression with an infinite/highest possible ratio) the drum room/ambience/overhead mics fairly hard, with fast time settings, a high ratio and low threshold. If you’re working with programmed or electronic drums rather than a live kit, programming a constant pattern of splashy cymbal hits and compressing with the settings above can work really well to loosen up and excite the groove.

Guitars

Distorted rock guitars often don’t need any compression at all, as anything heavily distorted will already have been leveled out dynamically by nature of the distortion process. For cleaner or acoustic guitar, start with a 2:1 ratio, and perhaps 4:1 for non-overdriven electric guitar, with a low threshold. To get a good sustain, start with a 4:1 ratio, fast attack and slow release. Then play the note you want to sustain, and raise the ratio until the sustain is as long as you want it.

Synths

Synth parts can also often be left alone, usually because their dynamics are generally already shaped at the programming stage to fit the role of sharp lead or more static pad, for example.

Using A Compressor In The Mix: Fixing Balance Issues Basic Dynamic Range Adjustment Walk-Through

At this stage we’re primarily concerned with controlling stray peaks on individual sounds, or bringing up the body or sustain of sounds: compression in it’s classic application, reducing the dynamic range of parts so that they each have a more consistent level, and so are easier to balance against each other.

1. First, concentrate on the balance. Can you hear everything you need to? Are there any

parts which aren’t coming through clearly or stick out of the mix too obtrusively, no matter where you position their fader level? When you can’t find a good static fader position for a part,

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Get That Pro Sound - The Ultimate Guide to Compression it’s a sure sign that some compression (or multing, see the box below) is in order.

When To Mult Tracks Rather Than Compress

Multing is a simple DAW technique of copying audio parts to an additional track (or just duplicating the whole track) and then adjusting the level of particular notes and phrases to make the overall level more even – thereby potentially avoiding the need to use compression or level automate level changes. Multing can solve a lot of problems on its own, but quickly gets very fiddly if you try to use it to deal with lots of short-term balance problems (lots of single notes or words that are too loud or quiet), and this is where the automatic processing offered by a compressor can be the better or complementary option. For example, you could mult out a guitar solo from the main guitar track to give it a higher fader level, but still compress that solo so that a few over-zealous notes don’t pop out too far. Try multing to solve balance problems first, but don’t be afraid to reach for a compressor when it suits the job better.

2. Insert Your Compressor and Select A Preset. Now insert your chosen compressor into the channel in question. An option here if you want to work quickly (which is likely when working with a alrge number of tracks in a mix) is to start with a likely-looking preset setting in your compressor. There’s no need to give it too much thought: it’s just to get you in the right ballpark with minimal tweaking, and you can then make any necessary adjustments next. 3. Set Threshold And Make-Up Gain. To start with, bring the threshold down low, so that the

gain reduction meter shows at least 6dB of compression on the loudest peaks. Then adjust the make-up gain (or equivalent output level control) to bring the overall level roughly back up to the pre-compression level.

4. Check New Level – Problem Solved? At this point, you may have solved the balance problem

without any further adjustments necessary. Play back your mix again and see if you can now balance the compressed track better. Yes: If you have indeed fixed the balance issue, just try gradually bringing the threshold back up and seeing how little compression you can get away with. Pushing your channel compressors too hard is a common mistake that can slowly suck the life out of a mix if it’s duplicated across all your tracks, so it‘s a good idea to keep the touches of compression as light as possible at this stage. Remember, use a little compression at various stages, so that the effect is cumulative rather than shovelled on in one go. No: If the balance problem is still there, try bringing the threshold down further, to see if that makes it easier to find a decent fader level. Feel free to completely max out the control if you like, even it if makes the result sound rather unnatural for the moment: the important thing is to keep concentrating on the balance, and whether the compression can deliver the static faderlevel you’re after. Be bold and loose with the controls here, making fast, robust changes to the controls as you sweep around and keep your ear out for the sweet spot where it just seems to

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Get That Pro Sound - The Ultimate Guide to Compression naturally come together.

5. When compression does solve your balance problem, ask yourself a follow-up question: do I like the subjective ‘sound’ of my compression? If not, try a few different compressors or presets. There will be times when although you’ve found an appropriate balance through heavy compression, the processing isn’t doing nice things to the instrument’s sound. Perhaps it’s making the performance feel lumpy and unmusical, or altering the tonality in some undesirable way. In these cases, just switch to a new compressor or preset, set it up as before and see if this one works better. Remember the different types of compressors discussed earlier, and how they’ll work slightly differently to each other on the same material. With experience, you’ll soon build a shortlist of personal favourites for different instruments. 6. If you still can’t find a static fader position that works, you probably need to do some other

processing or automation work to reach a decent balance. See the box below on EQ.

Compression, EQ And Effects Chains: Which First?

Pre- or post-EQ Placement Of Compression In The Effects Chain If you use a chain of multiple processes on an instrument, you might wonder where you should put the compressor. In this common scenario, it is usually best (all other things being equal) to put it first in the signal chain, for two reasons. One is that other effects can introduce more noise into the system, so if you put the compressor after those effects, you will end up amplifying that noise as well. The other point is that putting the compressor first in the chain also gives the other effects a better signal to work with. Should Compression Be Pre- or Post-EQ? A key exception of the above advice is when chaining compressors and EQ, as the difference between having the compressor before the EQ section or after it can be surprisingly large. Equalisation is primarily about changing signal levels, albeit in carefully specified frequency regions, so pre-compression EQ (i.e. changing the level of certain frequencies) can alter the way the compressor responds to the input material. Post-compression EQ won’t have any effect on how the compressor behaves. So essentially, if you’re happy with the way your compressor is working, just put any EQ after it in the processing chain. But if you find that frequency-based problems make it difficult to achieve the compression you want, that’s the time when pre-compression EQ makes sense.

Typical Compression Scenarios – Taming Excessive Peaks or Routine Dynamic Range Reduction – The Importance Of The Ratio Setting

Here are a couple of examples of typical compression scenarios you’ll encounter at this stage in your mixing.

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Scenario 1: Taming excessive transients/peaks by isolating them from the remaining notes with the threshold setting, and then a high ratio to clamp them down to a level more consistent with those remaining note bodies. What compressors do is reduce the amount by which a signal level exceeds the compressor’s threshold level, so in this case you want your compressor to put up a proper fight and all but stop the input signal from exceeding the threshold. That way you can set the threshold just above the level of the majority of the bass part, and it will then kick in at full force only when the over-zealous slap notes hit. Setting a compression threshold above the majority of the note peaks allows you to compress just the rogue slap note, but if you used a normal moderate compression you wouldn’t be able to contain it as well as you might like. Increase the ratio higher, though, and the gain-reduction will stamp down much more firmly on the offending level spike, preventing it from leaping out unduly within the mix. Scenario 2: Preserving the internal dynamics of a part with a lower ratio, that will squeeze the entire dynamic range just enough to position the part easily within a mix balance. In contrast to the above example, lower ratios tend to be better for instruments which have good musical dynamics, but simply have too wide a dynamic range. Compressing with a low ratio can be used to gently squeeze the dynamic range such that it will maintain its position in the mix balance. However, if the ratio is set too high, the compression will iron out the part’s internal performance dynamics and render it unmusical. Imagine an electric guitar part where there are no dramatic level spikes, but where the overall dynamic range is still making it difficult to balance in the mix with a static fader level. You want your compressor to act more gently on signals overshooting the threshold level, so that you can set the threshold just above the level of the softest notes and then subtly squeeze the whole dynamic range down to a more manageable size. It’s a compressor’s Ratio control that allows it to tackle these two contrasting problems, effectively setting how firmly the compressor reins in signals that overshoot the threshold level. At low Ratio settings (something like 1.5:1) the overshoots are nudged gently back towards the Threshold, whereas at higher settings (12:1, for instance), overshoots are clamped down on without mercy. At the highest Ratio settings (some compressors offer infinity:1), louder sounds are effectively stopped in their tracks, unable to cross the Threshold at all. So for our first scenario, a high ratio is just what is needed. For routine dynamic-range reduction tasks like that in the second scenario though, lower ratios (up to about 3:1) will fix balance problems in a more natural-sounding way. In scenario 1, you’d set the Ratio up fairly high to start with, and then find a Threshold setting that caused the gain reduction to kick in only on the excessive peaks. Once you’d done this, you’d listen to ascertain whether you’d solved the balance problem, and then adjust the Ratio control accordingly. Still too much slap? Increase the ratio to clamp down on the peaks more firmly.

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Get That Pro Sound - The Ultimate Guide to Compression In scenario 2, you might start off with a fairly low ratio of around 2:1 and then set the Threshold so that gain reduction happens for all but the quietest notes. With the Threshold in roughly the right place, you could then turn back to the Ratio control and tweak it one way or the other to achieve your static fader level. If some quieter notes are still too indistinct, increase the ratio to reduce the dynamic range further. Why not just max out the Ratio control? The danger is that if you turn it up too high, you’ll iron out the important performance dynamics that make the part sound musical, leaving it a bit flat and lifeless – so try to turn up the Ratio control only as much as is required to get the balancing job done. At this point you might be thinking: what if I needed not only to apply high-ratio control on the loud peaks, but also more general low-ratio dynamic-range reduction on the same sound? The answer is by chaining more than one compressor in series. This is quite common in practice, and lets you dedicate each specific compressor to a different task. If you’re wondering what order to put the different processors in, though, the answer isn’t quite as clear. The best solution is to try both ways and choose the one that best resolves the balance.

Stage 2: Using additional compression for colour and creative dynamics

Having resolved any pressing balance problems, you might now want to go back to certain tracks that you feel could use additional character, punch or energy. Now’s the time to reach for the tube and analogue-modelling compressors. You may want to simply adjust the compressor that you’ve already used on a given part; but be careful that you don’t undo your correctional work from before. A better option would be to simply insert another compressor after the first, dedicated to providing extra character and dynamic shaping. However, when you consider putting two compressors on every main track, things can get overly complicated (and very processor-intensive!) very quickly. This is why it’s such a good idea to, at this point if you haven’t already, set up groups or busses for each main section of instruments and tracks – usually one each for Drums and Bass, Synths and Guitars, FX, and Vocals (including the appropriate combination of lead, backing and harmony parts). Now you can apply that creative/character compression to all the drums, for example, at once, with one compressor instance. This is a huge benefit, as the dynamics processing applied to a group of instruments in this way has the effect of ‘knitting’ or ‘gluing’ them together – one of the great strengths of compression in a mix context. It’s especially effective for enhancing the groove of the drums as a whole, and of the drums and bass together. So, route the individual tracks to the relevant group or buss; insert a compressor on the group, and start applying ‘submix compression’.

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Using A Compressor For Character/Distortion

One of the most effective areas in which to apply character compression is drum parts. As already mentioned, almost any processing on drums comes off as some kind of ‘effect’, and so you can get away with relatively extreme settings. A popular technique is to intentionally clip, or overdrive the drums compressor in or output: this usually adds a certain ‘crunch’ or bite to drums that makes them feel really powerful. (Don’t worry, in this case it sounds more like a boost in the upper-mid frequencies than ‘distortion’ per se – it also affects the balance between the attack and the ring of the note in a generally useful way). Of course, it’s a great way to introduce some authentic vintage character to programmed or very clinical-sounding drum parts. The typical approach is to push the Input or Output/Make-Up Gain to drive the compressor (or the next device in the chain, such as tape, an analogue-emulation plugin or a second compressor or limiter) into clipping. It’s worth noting that the effect can be achieved without actually applying compression (since the main task for the compressor here is to simply raise the gain level), but if you do want to actually apply compression at the same time, just make sure that the compression/distortion is consistent (ie. low threshold) across the whole sound being processed, because we are using it like EQ: for a color change. The Waves Renaissance Compressor is a good choice for this role because it allows a large excess of Make-Up Gain to be applied, which tends to clip the output. You can also try inserting two Renaissance Compressors in series, which allows more variations in drive color.

Character Compression Case Study: Working With A Snare Drum

Let’s mess about with a single snare drum hit to demonstrate the sorts of character changes you can make with compression. Armed with these parameter combinations, you’ll be able to create many different effects from a standard snare hot, from tight and punchy rock snares, massive dubstep snares, breathy snares and snappy pop/R&B snares.

A. Fast attack, fast release – Transient suppressor

Set the attack time to fast and the compressor will respond quickly to the fleeting initial drum transient, reducing the gain swiftly. If you then set the release time very fast, the gain reduction will also reset very rapidly — well before the drum sound has finished, such that the lower-level tail of the drum hit won’t be compressed as much. The drum transient will be de-emphasised relative to the overall snare sound.

B. Fast attack, slow release – Overall level change; little character change

If you partner your fast attack with a slower release, the gain-reduction will reset very little during the drum hit itself, instead resetting itself mostly between the hits, so the balance between the transient and sustain phases of the drum will remain pretty much unchanged. The

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compressor in this case is simply making the level of each drum hit appear more consistent.

C. Slow attack, slow release – Transient booster

However, if you then set the attack slower, you’ll find that some of the drum transient begins to sneak past the compressor before its gain reduction clamps down, effectively increasing the level difference between the transient and the rest of the snare sound. So working mostly with the attack and release controls we’ve achieved three different balance results — less transient level; more consistent hit level; and more transient level — all with the same compressor, and potentially all from the same snare sample/recording! Of course, it’s a good idea to pick sounds that are at least close to what you want to begin with – but this shows you that with compression you can sculpt your sounds in a completely different way to EQ, for example.

Compressing Submixes

Once you’ve routed all the individual tracks to it’s corresponding submix, you can compress the instruments in each submix together. Remember, using compression in a mix is all about the cumulative effect – if you’re after an exciting, hard-compressed sound, things will always sound better if you apply moderate compression at several points between the individual tracks and the master output, than if you just plaster a final stereo mix to the wall with heavy compression right at the end. Submix compression is also useful because it’s another point in the mix where you can maintain your relative levels and frequency balances – one of the reasons that people resort to multi-band compression (see below) on the master buss is that they’re trying to do too much at the final stage, and when they apply as much compression as they want all in one go, they get the side-effect of the compression unbalancing their carefully constructed mix. Instead of reaching for a multi-band compressor to compress each of the frequency bands individually to maintain the balance, it’s much better in the long run to simply compress in sections over the course of the entire mix.

Drum Submix Compression

A great place to start is usually to compress a submix of the drums, possibly together with the bass and the drum reverbs. A gentle approach on the submix here can lock in the sound of the kit with it’s ambience/reverb, and also get the bass and drums grooving like the single rhythm unit we want. Bare in mind that the compression will affect the balance of the drums in relation to each other, so it may be easier to ‘mix into the compressor’ – insert and set the compressor first, and then rebalance the parts while listening through the compression – rather than applying it as a last step. In practice, this means some interplay between setting the basic drum sounds and mix and setting the right overall compression, which can be tricky at first. But the

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Get That Pro Sound - The Ultimate Guide to Compression results and sense of control you gain over your mix is absolutely worth it.

Rhythmic Compression On The Drum Submix

Another reason for compressing the drum submix is that it allows you to introduce or accentuate the overall groove, by ‘tuning’ the compressors attack and release to work in rhythm with the tempo and spacing of the drum hits. Here’s how:

1. Start with a high ratio and low threshold so that the signal is heavily compressed, with a

large amount of gain reduction indicated on the meters.

2. The pumping or breathing effect is dependent on the attack and release controls. Set the

fastest attack possible, and release to the slowest. Now move the release control through its range to its fastest position and note how the sound changes. You’ll hear rhythmic compression effects at fast release settings.

3. With the release now on a fast setting, move the attack control for slower attack times and

note how the sound changes. The relationship between the two controls will give many sound variations, and it should be possible to get the compression turning on and off in time with the beat.

4. Once you’ve got a sound you like, use the Output/Make-Up Gain to set the output level back to something appropriate for you overall balance. Advanced compression: Sidechaining & Parallel Compression

If you’re going to use any advanced routing or compression techniques, now would probably be the best time to implement them (more on this in the next chapter).

Stage 3: Stereo Mix Compression Toggling the Master Output Compressor On & Off During Mixing

Having a stereo compressor over the whole mix is generally a good idea, but monitoring through it when mixing is hard work. While it can be useful to know what the final compression will do to the mix, you’ll probably just be fighting it the whole time. Leave it bypassed until the mix is almost finished. Even if you’ve compressed individual tracks and submixes gently up to this point, when compressing a whole mix with a regular stereo compressor, it can still be easy to go too far and mess with the overall dynamics, because ultimately the compressor responds to the peak signals regardless of frequency range – the loudest/peak signals are generally to be found in the lower frequencies (as it takes more sonic energy to create a ‘loud’ bass sound than a higher pitched one), so you will tend to get audible pumping of the higher frequencies every time the kick sounds, for example, if your mix compression is too heavy. One solution is to have the master output compressor set up right from the start of your mix, and ‘mix into’ it in the same way as already mentioned regarding submixing. This does require setting up appropriately moderate compression right from the beginning – try a ratio of only 2:1 at first. This way, all the balance

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Get That Pro Sound - The Ultimate Guide to Compression adjustments you make along the way will not be undone when you get to the master output, because you’ve taken the additional compression into account all along. The downside is that it can be hard work monitoring constantly through a mix buss compressor, and there will be times where you’re fighting against it in your efforts to balance and apply other processing to parts – so make sure that you regularly bypass the mix buss compressor as you mix and monitor, double-checking that it’s helping and not getting in the way. If you find that no matter what you’re doing you’re not getting the results you want with a submixes/stereo compressor on the mix buss strategy, you could try a multi-band compressor.

Multi-Band Compression

As already mentioned, when working with material that covers a full (or at least large) frequency spectrum, such as a complete mix, normal compressors tend to introduce a ‘pumping’ effect with anything more than very subtle settings. This is because the lower frequencies which tend to trigger the compressor will normally be doing something quite different to the higher frequencies, yet the compressor will attenuate the entire output by the same amount based on the loudest parts, regardless of frequency. Multiband compression, as the name suggests, uses ‘crossovers’ to split the full-bandwidth input sound into sections of smaller bandwidths, which are then compressed separately. This way you can compress the lower frequencies harder than the highs, for example, the result being a louder, tighter mix which doesn’t pump or sound squashed. The reasons why multi-band compression is not always recommended are that there’s even greater capacity for error than with regular compression – knowing where to place the crossovers, how much to compress each band in relation to the others, not undoing the good tonal balance you’ve achieved up to that point etc. all take some skill and experience. There’s also the idea that splitting up the full mix into separately processed parts again at this late stage, when you’re generally trying to get everything gelling together, is not going to bode well in principle. I would never say ‘don’t ever use multi-band compression’, just be aware that if you construct your mix well in the first place you won’t need it other than in exceptional circumstances.

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Advanced Compression Techniques Parallel Compression Also called ‘stealth’ and ‘invisible’ compression (as well as ’New York’ compression because of where the technique first became popular), parallel compression is a lot simpler to set up and get good results with, than it is to understand why it works… Just to recap, one of the main uses for compression is to increase the apparent loudness of an instrument or mix. Compression works by reducing the high signal levels, bringing them down closer to the low-level passages, and then applying make-up gain. Thus the low-level signals are brought up and the whole thingl sounds louder and ‘fatter’. This is fine in theory, but as we’ve spent much of this guide discussing, the trouble is that the effects of compression, particularly the sort of heavy compression you might want to use on drums and vocals, are quite audible, which often means a compromise between getting enough compression and not losing the dynamics of the original sound. What we need is compression that only operates on low-level signals (where the details are), making the quiet sections louder without affecting the loud sections. The answer is suprisingly simple: you mix the uncompressed signal with a compressed version of the same. At levels below the compressor’s threshold the two signals will combine, producing a straight 6dB increase in level. But above the threshold the compressed signal will be progressively reduced and add hardly any additional level to the mix. Put another way, the compressed version dominates at low signal levels and the uncompressed version dominates at the audio peaks.. The result is a form of compression where the sound is reinforced only where it needs it: therefore, you can get more overall dynamic range reduction with fewer audible sideeffects. The dynamics in the dry signal are preserved while the compressed signal adds body and character to the overall sound. It works for any instrument (try it on drums, vocals, rhythm guitars and of course whole submixes), and the added character can really bring a track to life. Once you know the principles of parallel compression, there are a couple of different ways to go about setting it up. Neither is better: they are just different ways of reaching the same result.

Parallel Setup 1:

Simply duplicate (aka ‘mult’) the audio track that you want to parallel compress, and insert the compressor on the duplicate only.

Parallel Setup 2:

Set up the compressor on a group/buss, and send a bit of each of the instruments to be parallel compressed to that buss. This allows you to pass many tracks through the same compressor, handy for fattening related tracks together, and of course saving on processor power.

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Parallel Setup 3:

You can use the mix or wet/dry knob if your compressor plugin has one, to strike the right balance between compressed/uncompressed signals.

Typical Parallel Compression Starter Settings

We’ve already looked at typical settings for various key instruments, but here you’re likely to want to use – and can get away with – much more extreme settings than if you were compressing normally. Parallel compression settings can vary quite radically (it’s something of a stylistic effect as much as anything), depending on the exact effect required. Mix engineers often go for a more characteristic effect by using a high ratio and fairly fast attack and release times while mastering engineers, on the other hand, might use much more gentle ratios and longer release times for a more subtle ‘massaging’ of a full mix. However, a good general-purpose / subtle setting could be: Start with a 2:1 Ratio, Hard Knee setting, fastest (0ms) Attack and Release around 350ms. Turn off the Auto Gain mode if your compressor model has the option, and while listening back to your mix set the Threshold low enough that you’re getting about 20dB of gain reduction (as we said, you can go more extreme than with normal compression). Finally, adjust the MakeUp Gain of the compressor to get the most suitable level of compressed signal for your needs. At this stage it’s also a good idea to toggle the mute button on and off, to compare the subtle sonic properties of the processing with the untreated original signal. If the processing isn’t quite working for you, try tweaking the compressor’s release time, as this can have quite a pronounced effect on the sound of the processing.

Example: Parallel Compressing The Drum Submix 1. First, lightly compress (0.5-1dB gain reduction) the kick and snare as you normally would. 2. Mult the kick and snare to another group: this will be our parallel compressed group. Apply

strong compression (10 or 12 dB of gain reduction and a Ratio of between 4:1 to 8:1) and bring them up underneath the originals. Set the Attack as slow as possible and the Release as fast as possible, so that all the transients are getting through and the initial punch is still there, but the compressor releases instantly when the signal drops below the Threshold.

3. Then send all the main dry drum tracks – kick, snare, toms, but not the rooms or overheads –

through another parallel compressor and bring that in as well, to give the kit an overall sound.

Other Considerations

Different attack and release times create different effects, as do different ratios. Using a fast attack and slow release removes all the transients from the signal. However, with a shorter re-

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Get That Pro Sound - The Ultimate Guide to Compression lease time, you can create that distinctive rhythmic ‘pumping’ effect. Also remember that different compressors have different characters, and these become particularly apparent when a compressor is pushed to the kinds of more extreme settings used for parallel compression. Try all kinds of compressors, saturation plugins and distortion units – for example, bitcrushers and really distressed effects can add something amazing when mixed at low levels under the original dry part.

EQ + Parallel Compression = ‘Custom Enhancer’

One thing you may notice when experimenting with heavy/parallel compression is that it can make the bass frequencies of processed audio seem weightier, particularly if you try processing complete mixes (refer to the earlier section on multi-band compression for the explanation of this). If this isn’t a desirable side-effect for your purposes, you can use insert an EQ before the compressor to adjust how the compressor is responding. Just set a high-pass filter and sweep up until the frequency balance of the compressed signal is more what you’re after. An extension of this filtering technique allows you to simulate the effects of a typical Enhancer processor, used to add psychoacoustic high-frequency ‘sparkle’ to sounds). Raise the filter frequency of your EQ such that only very high frequencies are allowed to pass — try 7kHz as a starting point — and reduce the compression threshold to retain similar levels of gain reduction and you’ve essentially got an enhancer. Just remember that it’s easy to overdo: use the bypass regularly, or you’ll end up with a tinny sound that’s unnecessarily tiring to listen to. A yet more convenient way of implementing EQ on a compressed signal is to engage the Sidechain EQ on the compressor itself. Which leads us nicely to:

Sidechain Compression What Is A Sidechain?

The sidechain, or key, is the signal within a compressor which monitors the input and controls the output level. On some compressors this will appear as an extra input labeled ‘Sidechain’, but in others there will also be a whole host of side-chain processing options, most commonly some kind of EQ or filter. If the compressor has an external sidechain - or key – input, you can use the characteristics of one sound source to compress another. This is how you can use a kick drum track to make a synth pad pump in time with the music. When you understand the creative and technical possibilities of using the sidechain in dynamics processing it opens up all kinds of creative possibilities, as well as new solutions to typical mix problems.

Compressors With Sidechain EQ

If your compressor does have a Sidechain Filter or built-in EQ, you’ll find that in practice it’s

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Get That Pro Sound - The Ultimate Guide to Compression much more than just another type of EQ: instead of simply cutting or boosting different frequencies, you can allow different frequency bands to control the amount of compression applied. When you are having trouble getting that elusive punchy, powerful sound, and EQ and compressor plugins in series don’t seem to be delivering the results, EQing the sidechain may be the answer.

Rhythmic Pumping Sidechain Compression

Probably the most recognisable creative use of compressor sidechains, this is the effect created by applying heavy compression to a fairly constant, sustaining sound (like a synth pad or bassline) with a compressor whose sidechain is being ‘fed’ by a completely different sound – usually a kick drum or kick/snare drum submix in modern electronic music styles. Every time the kick hits the synth dips in volume, creating a pumping effect that can be very effective for adding apparent energy and dynamics to a dance production. It’s now accepted to hear a lot of modern electronic music – techno, house and trance particularly – with the full mix pumping dramatically. It’s easy to overuse the effect, but it really does add so much energy and excitement and, to a greater or lesser degree, it’s expected of a lot of modern productions.

1. To use this technique, first create a 4/4 kick drum pattern – the basic House pattern – and loop it for as long as your track is. You can mute this kick drum track if you already have a kick in your mix: it doesn’t need to be audible in the mix as it’s only there as a source for the sidechain of a compressor that’s operating on another sound. 2. Insert a compressor with an external side-chain capability, and select the kick drum track as

your input source.

3.As far as settings for the compressor itself, there are no rules here! Start with quite extreme settings: as usual, the higher the Ratio and lower the Threshold the more extreme the overall compression will be. Try a fast Attack with a medium Release, but adjust depending on how much you want the track to pump. Once you’ve got the amount of pumping about right, return to the Ratio and Threshhold and adjust them to taste. 4. To make the effect even more dramatic, and perhaps more of spot effect, try inserting a reverb before the compressor. This will emphasise the pumping nature of the effect, as the compressor has more dense, sustained sounds to breathe in and out.

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Bonus Compression Pro Tips 1. On The Attack

Try not to use the fastest Attack on everything if you can help it: many instruments, particularly guitars, will stand out more with the extra ‘front’ you get from allowing the initial transient/attack through a compressor unscathed. Bass instruments can really benefit from the extra definition provided by a good attack transient, allowing them to punch through a dense mix.

2. The Fast Way To Build A ‘Personal Favourites’ Compressor Plugin List

Which compressors in your collection are the best for which instruemtns and situations? Insert multiple compressor plugins on the same track (e.g. the snare drum track) in your current mix, and solo them one at a time, paying attention to the character differences between them. Once you’ve programmed a few of them, do some A/B comparisons and decide which you like best for different effects. Also try listening back to each compressor with the track both solo’d and in the context of the entire mix: as ever, what sounds subjectively ‘better’ can be very different depending on whether you’re listening to it in isolation or in a mix context.

3. Compressing Effects Returns

Don’t forget that effects returns – particularly reverbs and delays – are just as fair game and in need of compression as any of your individual instrument tracks. For example, if your delay doesn’t quite fade away as you’d like, or you want to bring up and draw out the sustain of a reverb tail, then compressing the return (i.e. seperately from the instrument that fed the delay) may give you the control you’re after.

4. The Relationship Between Attack/Release Times & Gain Reduction

An important consideration when tweaking and finetuning compressor settings is that changing the Attack and Release times will affect the amount of gain reduction that you get for a given combination of Threshold and Ratio settings. For example, a side-stick sound (i.e. a sound with a short transient and very little sustain) might completely bypass a compressor that has a long attack, even if its level shoots way over the compressor’s threshold. For this reason, it’s common to keep adjusting Threshold and Ratio controls alongside your Attack and Release. Always remember the interrelated nature of all the controls and settings on a compressor.

5. Using Compressors In The Real World: When To Use Eyes And Ears

When talking about compressor settings, it’s necessary to describe things in milliseconds and other particular numeric values. However, don’t get too hung up about using ‘exactly the right settings’: suggested settings are only ever hypothetical averages, and as such only a rough guide to how a specific compressor might respond in practice. A better approach is to simply listen,

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Get That Pro Sound - The Ultimate Guide to Compression and focus on finding the best balance with the fewest unmusical side-effects, adjusting the Attack and Release controls by ear. Having said that, one situation when you will want to trust your eyes is when reading a compressors gain reduction meter: this will show you how much actual compression is being applied, and how fast the compressor is responding with it’s current settings to the input material. This is very useful for offering visual clues as to whether the compressor is doing what you want.

6. Be Aware Of Your Release Time Setting

Release is the time it takes for the amount of gain reduction to return to zero after the signal has passed back below the compression Threshold. In some instances, the signal might never pass below the Threshold long enough for the level to begin to return to normal, to any significant extent. The result here would be, for example, 30dB of gain reduction, but not 30dB of compression. You don’t need a compressor to get any amount of gain reduction – if that’s all you’re after, just lower the fader! ‘Compression’ implies a constantly changing amount of gain reduction, with the gain reduction meter visibly dancing up and down. If it’s not moving, you’re not compressing. How fast it dances up and down is up to you but, if you want value-for-money compression, a short fast Release time will give you a more audible compression effect. A slower Release will lessen the audibility of the compression, but you also won’t actually get as much real compression.

7. Set The Threshold Only As Low As Is Actually Needed To Avoid Over Compression

This is related to the tip above. Don’t forget that after initially setting a low Threshold in order to hear clearly what effect your other control adjustments are having, unless you’re after a particular effect you should generally draw the Threshold back up as far you can get away with for lean, anti-side-effect compression. Imagine a scenario where an instrument plays occasionally with silences in between: this is where over-compression is most likely to happen. When setting the Threshold, many users have an idea of how much gain reduction they want to hear (and see on the meter). The amount of gain reduction is controlled by both the threshold and ratio controls. Suppose these controls are set so that the desired amount of gain reduction e.g. 12dB is achieved. This should be fine shouldn’t it? Look again at the gain reduction meter. While the instrument is playing, does it ever go all the way down to zero? If it doesn’t, if it only goes down to 3dB, then you haven’t applied 12dB of gain reduction, you’ve actually only got 9dB of compression/ gain reduction. The other 3dB could have been achieved by simply lowering the fader. This, in itself, isn’t necessarily a problem. The problem is that, when the instrument starts to play, the compressor has to go all the way from zero gain reduction to the full 12dB. The necessity of covering that additional 3dB will audibly distort the initial transient. Try this out and you’ll hea it. This leads to rule number one of gain reduction - at some point in the course of the track while the instrument is playing, the gain reduction meter must indicate zero, otherwise the minimum

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Get That Pro Sound - The Ultimate Guide to Compression reading obtained shows wasted gain reduction and over compression, leading to the distortion of transients that follow silences.

8. Macro vs. Micro Compression: Setting Correct Attack & Release Times

Imagine a scenario where we’re mixing a song with a strummed acoustic guitar. The guitar has a nice, natural sustain that works really well when it’s at the right level in the mix, but you find that you have to turn the fader down whenever the player digs in more during the chorus. So, you quite reasonably insert a compressor to even out the level difference between song sections. However, when you actually start dialling in compression settings you find that, rather than just reducing the level differences on the ‘macro’ scale, between song sections, the compressor is also evening out the much shorter-term, ‘micro’ level differences between the attack/ transient and sustain parts of each strum. So although you’ve sorted out your overall balance problem, the unacceptable side-effect is that the impact of each strum is softened, or the instrument’s sustain is over-emphasised. The Attack and Release controls provide a remedy here, because they determine how quickly the compressor’s gain reduction reacts to changes in the input signal level: the Attack setting specifies how fast the compressor reacts in reducing gain, while the Release specifies how fast the gain reduction resets or ‘releases’ the signal. The reason why the compressor in our example isn’t doing the job we want is that it’s reacting too fast to changes in the signal level: the Attack and Release times are too short. Increase these and the compressor will react more slowly, which means that it’s likely to deal with this particular balance problem more effectively, because it’ll track longer-term level variations (such as those between our verse and chorus) rather than short-term ones (such as those between the individual strum transients and the ringing of the guitar strings between them).

9. When Compression Isn’t The Magic Bullet: Knowing The Limits Of Compression

There are often situations where no matter which compressor you use, or how you set the Threshold, you can’t find a good fader setting for the track in the mix, even if you’ve already done some sensible multing. At this point it’s tempting to simply settle for a compromise between dodgy balance and unmusical processing side-effects. But listen carefully, because your mix is probably trying to tell you something: this situation requires something different than can be achieved with simple compression on it’s own. For example, balancing bass instruments in a mix is a classic tricky situation where you’ll typically need to use more than compression to achieve professional results. You’ll commonly find that if you bring the level of the bass up to where it’s cutting through adequately in the mid-range, it’ll also now be swamping everything else at the low end at the same time. Simply compressing the the bass at this point is unlikely to solve the issue, because no matter how much you reduce the dynamic range of the sound, you’re not fundamentally changing the balance of the instru-

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Get That Pro Sound - The Ultimate Guide to Compression ment’s frequency content. It’s much better to address a problem like this with EQ first – or possibly even replace the bass sound completely, if it’s a synth bass, or adjust your arrangement to make space for the midrange element of the bass. You’ll be able to tell when you’re on the right track with EQ when it starts getting easier to find a suitable fader level for the bass: then you can think about compression again, although by this point you might discover that compression is no longer required at all. Another very common occasion where compression can’t provide a complete solution to mix balance issues is when dealing with very critical tracks – lead vocals are a common example here. As powerful as compression is as a creative and technical tool, it’s simply not intelligent enough on it’s own to deal with extremely dynamic, detailed and complex parts like a main vocal usually is. If you try to keep these parts up-front and audible in a mix entirely with compression, they’ll usually sound over-processed; it’s more sensible to keep the compression within musical-sounding limits before dealing with fine, moment-to-moment level tweaks manually, with vocal fader automation. As with many things, getting the best results from compression also means understanding it’s limitations.

10. Using A Compressor Followed By A Limiter For Real Clipped Punch

Following on from the previous tip, there’s another particular scenario where compression is only half the answer: in increasing apparent loudness. One of the significant characteristics of compression is that it works optimally over periods of at least tens of milliseconds: If you try to make a compressor respond too fast by using very short attack and release times in your quest for total loudness), the compressor begins to respond to individual waveform cycles rather than the greater overall shape of the signal, and you start getting distorted lower frequencies (kick drums and bass in particular can appear to lose bass content with Attack times under 50ms). Clearly, there are limits to using a compressor for loudness. The answer can be to use a compressor together with a limiter, in series. Limiters work in microseconds, which can make all the difference, and the nice ‘soft clipping’ type of harmonic distortion generated by valve designs (and valve-emulating plugins) rounds rather than clips the peaks – which conveniently increases perceived loudness. A limiter will only introduce soft clipping on high-level signals, so by using a compressor followed by a limiter, you can allow each of them to play to their time-based and amplitude strengths. The compressor evens out the overall level of the signal, not clipping the peaks but bringing them to to a more uniform level (you don’t have to worry about compressing the peaks anyway, as any that do spill through will be reined in by the limiter that’s next in the signal chain). This is just the sort of raw-but-optimized audio a limiter likes – it simply has more signal to work it’s soft clipping magic on, for achieving maximum overall ‘loudness’ gains without unwanted side effects. You can set up increasingly elaborate/flexible versions of this configuration: for example, you

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Get That Pro Sound - The Ultimate Guide to Compression might very well want to combine the compressor/limiter series with the benefits of Parallel Compression described earlier. In such a series-parallel configuration, the compressor first smooth’s out and brings up the levels; the limiter soft clips the peaks; and the result of that whole process is added back to the uncompressed signal. It might sound like overkill for some, but the result is highly controllable enhancement over a wide range of levels. If you want to go further still you might add an EQ after the compressor, so that you can choose the specific frequency range to be affected: with this setup you can add just the right hint of distortion without going over the top, particularly in the mid-range.

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Conclusion

Throughout this guide we’ve covered everything from quickly and effectively setting up compressors for a range of typical duties, to plotting and implementing an overall compression strategy, to some advanced techniques for creating refined, polished and ultimately professional mixes. If you haven’t already, have this guide in front of you and open (either in a window next to your DAW or printed out on your desk): this way you can refer to it as you work through the techniques and see how they work in the context of your own music. That’s what it’s all about. There’s a lot of information packed into this guide and it’s unlikely you’ll digest it all simply by reading cover-to-cover: by all means do that first to get an overall view of what’s covered, but after that you’ll probably get the most benefit by using it as a quick-reference resource as you develop your abilities.

I really hope this ebook will be helpful in your next sonic adventures - let me know how you get on with it at [email protected], and don’t forget to check out the GetThatProSound blog regularly for new posts, more tips and more ebooks... Best of luck, George Robinson Get That Pro Sound

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GTPS Compression Ultimate Guide

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