!ay 24, 2006 - Musicology Departmen" - #niversi$ of Gra%
Introduction
Psychoacoustics and Music Perception
In this interdisciplinary approach for the study of the timbre of the classical guitar, we distinguish between :
An Interdisciplinary Study of the Timbre of the Classical Guitar : Relating Gestural Control, Acoustics and Verbal Description of Guitar Tones
• instrument-dependent dimensions of timbre, relating to the structural components of the instrument (static) • performer-dependent dimensions of timbre, relating to the gestures applied by the performer on the instrument (dynamic) Starting point: an inventory of verbal descriptors (adjectives) commonly used by professional musicians to describe the brigthness, the colour, the shape and the texture of the sounds they produce on their instruments.
Prof. Caroline Traube Laboratoire d’informatique, acoustique et musique (LIAM) Faculté de musique, Université de Montréal, Québec, Canada
Comparison between the elementary units of speech and instrumental music: phonemes and notes
Performer
Gesture Primary feedback
Instrument
Acoustic signal
Listener
Verbal descriptors
Secondary feedback (auditory)
Comparaison of acoustical features
Comparison based on functional value - Phonemes are a set of universally accepted and understood symbols used to describe the sounds of a language as it is spoken. Phonemes transcribe the timbral features of a language, but not the pitch, the dynamics, the duration nor the speed of articulation.
De la musique avant toute chose - Notes on a score indicate the pitch and duration of the sounds the performer must play. Scores generally include dynamics as well. In Western instrumental music, timbral features are rarely notated.
« Speech and music, acoustics and coding, and what music might be ‘for’», Joe Wolfe (ICMPC Proceedings)
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The Ch’in (ancient Chinese seven-string lute)
« The flying dragon grasping its way through the clouds »
For this instrument has been developed a very complex timbre notation system including more than one hundred symbols.
This symbolic picture illustrating a finger technique for the Ch'in suggests that the touch should be broad and firm, the hand having more or less a clawing posture.
Robert Hans Van Gulik « The lore of the Chinese Lute »
from a Japanese manuscript copy of the Yang-ch'un-t'ang-ch'in-pu (Gulik, 1940).
The study of speech
Phonemes and notes as they are heard There exists a continuum of articulated sounds or utterances in which language and music exist as they are heard (Nattiez, 1990).
ALL SOUNDS ARTICULATED SOUNDS
Phonemes
Notes
Language
Music
Levman (1992) indirectly supports this idea in his discussion on the origins of music and language where he states that the differences between the performance of music and language are of degree, not of kind. Pitch, dynamics, duration and speed of articulation are all used in speech and in music, but their gamut is wider in music. Music may have evolved out of language and songs would then be exaggerated speech.
Phonetics and phonology Phonetics is the scientific study of the sounds of language and of the spoken
communication process. Phoneticists are more concerned with the sounds of speech than the symbols used to represent them. Phonology is the study of the function of phonemes in a given language and the opposition and contrasting relations in the system formed by the sounds of this language.
Production
Phonetics subdisciplines Articularory phonetics is concerned with the positions and movements of the lips, tongue, and other organs in producing speech
Transmission Acoustic phonetics is concerned with the acoustic properties of the speech sound
Perception Auditory phonetics is concerned with speech perception.
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Vowel space (F1-F2 plane)
The study of instrumental sound production : sonetics
Frequency of first formant F1
Sonetics is the study of music in its gestural, acoustical and psychoacoustical reality (Vecchione, 1990) : • articulatory sonetics is concerned with the relations between acoustical signals and characteristics of the signal-producing gesture • acoustic sonetics is concerned with the acoustic properties of the musical sound • auditory sonetics is concerned with timbre perception. By analogy with phonemes and phones, we can define : • Sonemes (from Latin sonus, « sound ») as sound elements in a musical instrument « language ». The soneme could be defined as an element in the palette of timbre nuances achievable on a given instrument, labelled with verbal descriptors such as round, dark, nasal, hollow, etc. • Sones as the objects of study in sonetics; the sones are the actual musical sounds as produced by performers; only the sones have an objective existence.
Frequency of second formant F2
Perceptual dimensions of an instrumental timbre space [Grey & Moorer, 1977]
Macroscopic view of timbre
Exploring the timbre subspace of the classical guitar aggressive dry
cold
glassy
narrow nasal
Microscopic view of timbre G
pointed thin
ponticello incisive explosive sparkling whole chocolatey warm velvety deep cavernous hollow wet
G = guitar
heavy dark soft estompé mat somber morne damped surd blunt closed
sugary tasto fleshy
percussive
metallic brilliant
round natural clear rich full opaque fat
large pulpy
creamy sweet smooth milky
thick
brassy resonating blooming
bright luminous
transparent skinny
cristallin sharp open
dense
voluptuous enveloping
Timbre verbal descriptors for classical guitar tones
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Instrumental gesture parameters for the guitar Plucking : excitation and modification gesture Plucking parameters • • • • • •
Position of plucking finger along the string Angle between finger and string (in an orthogonal plane parallel to the string) Angle between hand and string (in an orthogonal plane perpendicular to the string) Degree of relaxation of finger Weight of finger on the string Pick material (pick, finger or nail)
Fingering : selection and modification gesture Fingering parameters • • • •
location along string
Fret-string choice Finger pressure Vibrato Bending
brightness
?
vibrato
spectral flux plucking angle
Fingering points
Plucking points
Mapping articulatory timbre space and perceptual timbre space
attack time
Articulatory Timbre Space
Perceptual Timbre Space
nut x
bridge
x
tonehole
neck with frets
Influence of plucking angle on envelope decay rate (a)
If the plucking direction is
(c)
spectral analysis
(a) perpendicular to the soundboard, the decay rate is maximum. (b) parallel to the sound board, the decay rate is minimum.
(b)
Guitar : string plucked close to the bridge
(c) diagonal with respect to the soundboard, the decay rate varies, from a high value at the beginning of the note to a low value at the end of the note.
f
t Guitar : string plucked close to the middle of the string
spectral analysis
t
f
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Collecting verbal descriptors
Verbal descriptors for the timbre of the classical guitar
We asked 22 guitarists (university students at undergraduate and graduate levels in guitar performance) to define in writing 10 adjectives they commonly use to describe timbre. ss tne h g bri
More specifically, we asked them to :
ck pluse to le o l c neho to
1. Define each adjective by describing the nature of its corresponding timbre (how it sounds, what it evokes…)
estompé
[“Verbal descriptors for the timbre of the classical guitar”, Caroline Traube, Peter McCutcheon, Philippe Depalle - Conference on Interdisciplinary Musicology, Graz, 2004]
damped closed
The physics of an ideal plucked string Vertical displacement y of an ideal vibrating string of length l, plucked at a point p from an height h : l
p
h
warm
ck pluse to o l c nut
velvety
mat
hollow wet
surd
deep cavernous heavy dark
somber blunt
soft morne
cold percussive aggressive dry narrow nasal pointed glassy transparent thin skinny ponticello incisive brassy metallic resonating explosive brilliant blooming bright
sparkling
whole chocolatey
2. Provide synonyms and antonyms for each adjective. 3. Describe how each timbre is obtained (what gesture is used to obtain a given timbre)
ck pluse to e o l c ridg b
sugary tasto
fleshy
cristallin round sharp natural clear rich full opaque open fat
?
large pulpy
creamy
luminous
thick
sweet smooth milky
clusters of synonyms clusters of antonyms
Acoustic signature of plucking position p
l
Relative plucking position :
R = p/l Amplitude of nth mode of an ideal vibrating string of length l, plucked at a point p from an height h
With initial conditions :
R = p / l = 12 / 60 = 1 / 5
Amplitude of nth mode:
Shape taken by the ideal string over time after being plucked at 1/4 of its length from the bridge
Spectral envelope has comb filter shape
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Perceptual effect of plucking position
Comb filter “formants” First formant frequency :
A measure of brightness : the spectral centroid
F2 = 3 F1 F3 = 5 F1 F4 = 7 F1
odd formant frequencies only
etc... Variation of theoretical spectral envelope (magnitude in dB vs frequency in Hz) with plucking distance from the bridge (from 4 to 17 cm).
Since the product l fo = c (speed of sound), F1 is constant on a given string for a given absolute plucking position p.
Variation of spectral centroid (Hz) with plucking distance from the bridge (cm).
Perceptual analogies between the voice and the guitar FORMANTS ARE HERE
We suggest that: To establish perceptual analogies, it is not necessary to find strong similarities between the structures of the acoustical systems. It is sufficient to find similarities between the acoustical signatures of the sounds produced by those systems (i.e. between their effects) independently of their cause. VOICE : varying formants are due to variable resonators (mouth, tongue, palate change the shape of the vocal tract) GUITAR : varying formants are related to performer-dependent dimensions of timbre and not instrument-dependent dimensions of timbre!
source
filter
sound
FORMANTS ARE HERE
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Guitar vowels (spectra with “odd” formants) F2 = 3 F1 F1
To produce the stimuli, we asked a professional guitarist to play the same melody with different timbres.We selected four variations of the performance which were described by the guitarist as ponticello, brassy, round and tasto.
F2
F2
F1
F2
F1
F1
Nine French-speaking non-professional musicians and non-guitarists performers were asked to sing nonsense syllables that they felt perceptually close to guitar tones, associating a consonant to the attack and a vowel to the release of the tone.
F2
F1
Experiment: vocal imitation of guitar tones
F2
[ “Phonetic gestures underlying guitar timbre perception”, Caroline Traube, Philippe Depalle - Proc. International Conference on Music Perception and Cognition, 2004 ]
Stimuli
Results
Excerpt from « L’encouragement » for two guitars, Fernando Sor. Played by Peter McCutcheon.
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Listening to guitar sounds as vocal sounds
Applying distinctive features of speech to guitar tones
MIDPOINT
BRIDGE
shape of mouth
thin and nasal tones
round and open tones
hollow or closed tones
Mapping between - an instrumental gesture parameter (plucking position), - spectral content of sounds (formant structure) and - verbalisation (adjectives).
Sound color associated to each string First formant frequency :
Equal-value contours for three distinctive features of speech (OPENNESS, ACUTENESS, LAXNESS) in the (F1, F2) plane [Slawson, 1985]. The trajectory traced with a dotted line correspond to the relationship F2 = 3 F1, which is found for the first two local maxima of a comb filter.
Explaining guitar timbre verbal descriptors Among the adjectives commonly used by guitarists to describe timbre, we noticed that an interesting set refers to phonetic gestures. Applying some distinctive features of speech to guitar sounds, we can infer that the adjectives closed, round, large, open indicate different degrees of OPENNESS. The adjectives thin and round would be opposites along the ACUTENESS dimension. A warm or chocolatey sound would likely be associated with the maximally LAX point. Finally, a hollow or cavernous sound would actually sound like the [u] vowel produced as the mouth forms a hollow cavity. In conclusion, distinctive features of speech could be relevant perceptual dimensions of the classical guitar timbre space and can help to explain guitar timbre descriptors.
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