Voice-Leading Seventh Chords in Root Position Seventh chords almost always proceed down by fifth (or up by fourth, which is the same thing). Hence, three of the four methods for moving chords by fourth or fifth will also apply to seventh chords – with a few adjustments, as seventh chords must obey an additional rule. The seventh always replaces either the doubled chord tone (i.e., the root) or the fifth, and it must resolve down by step; note that when the seventh replaces the fifth, the chord is incomplete. The methods can then be sorted by which chord tone resolves to the third. Knowing which chord-tone the seventh replaces determines how to get into the seventh chord. The Tertian Leap method is a casualty of the seventh chords. Since the seventh must resolve to the third, the leap to the third that gives this method its name would create a doubled third, which is rarely permitted.
Common-Tone Method The common-tone method is best with an incomplete chord (otherwise, the resolution would create a doubled third – this is allowed here, but is not the preferred option). As with triads, the common tone (the root of the seventh chord) is retained; the third resolves upwards (as a leading tone, which it usually is). The seventh resolves downwards to the thirds (just as the missing fifth would otherwise have resolved upwards to the third). Complete the following progressions using the Common Tone method:
Triple-Root Method The triple-root method requires a complete chord. As with triads, the third and fifth of the seventh chord resolve inwards to the root on the next chord; the seventh resolves downward to the third, just as the doubled root would have done – in fact, the triad form is commonly transformed into a seventhchord form by treating the seventh as a passing tone to fill the skip found in the triad method. The leading tone (and the triad between third and seventh) is resolved correctly, at the expense of the final chord being incomplete.
Complete the following progressions using the Triple-Root method; if there is no seventh, add it as a passing tone:
Similar Motion Method The similar motion method works best with a complete seventh chord, and like the triple-root method, can be created from the triad form by passing tone. As with triads, it does not work when the leading tone is in the soprano. However, when the third is in other voices, this method is one of Bach’s favourites; it sacrifices the preferred resolution of the leading tone (and the tritone between the third and seventh of the chord) in favour of making both chords complete. Complete the following progressions using the Similar Motion method:
A Note About Tritone Resolution The interval between the third and seventh of a dominant seventh chord is a tritone. Normally, the third (which is also the leading tone) wants to resolve upward by step, and the seventh (like any chordal seventh) must resolve down by step. This agrees perfectly with the harmonic tension of the tritone, which wants to resolve inward by step in both voices if it is a diminished fifth, or outward by step in both voices if it is an augmented fourth. However, voice leading is all about compromise. Ideally, we want as many chords to be complete as possible. Unfortunately, when we have a dominant seventh chord resolving to a triad, it is not possible for (a) the seventh chord to be complete; and (b) the triad to be complete; and (c) the tritone to resolve correctly – we can have any two of those things at once, but not all three. The options, then, are to omit the fifth of the seventh chord, giving a doubled root; or to omit the fifth of the triad, giving a tripled root; or to allow the leading tone to skip down to the fifth of the following chord (only if it is in an inside voice). However, we cannot mess around with the resolution of the seventh, nor can we omit the root or third of either chord.
Combinations of Seventh Chords In chains of seventh chords in root position, it is impossible to for every chord to be complete and correctly resolved. Normally, every other chord is complete. The usual rule for chains of seventh chords is that roots become fifths (and vice versa) and thirds become sevenths (and vice versa). However, since the bass voice will always move from root to root, every second chord will be missing its fifth. This generally amounts to alternating the common-tone method with the either of the other two methods, except that the thirds do not resolve, but rather are carried over obliquely to become the seventh of the next chord. Complete the following chain of seventh chords by swapping 1 with 5 and 3 with 7.
Third-Progressions What is true of alternating triads is also true when one of the chords is a seventh chord: a chord alternation is begging for a third-progression in the soprano. The seventh of the seventh chord can participate in this procedure. It is also possible to create two third-progressions at once, in parallel thirds or tenths. Complete the following third progressions:
Remember that alternating chords should always be viewed as an opportunity for a third-progression, and conversely that certain third-progressions in the melody (such as – – ) strongly imply alternating chords.
3 2 1
Oscillating motion in one voice implies linear motion in the other (and, to a lesser degree, vice versa).
