Audio: voice leading (0:09)
voice leading plays a chord progression on a music box. The voice leading figure shows the score.
Voice leading, also called part writing, is a set of principles and procedures used in functional harmony to connect chords together.
Voice leading is another of those unintuitive phrases you encounter regularly in music. In essence, it refers to the way in which each note in a voice (or part) leads to the next in a chord progression. This innocuous sounding phrase hides its light under a bushel. Whole books have been written about voice leading and it is an issue of considerable interest in functional harmony.
Writing voice leading is the single most time-consuming task in writing music. The reason is that there is a tremendous amount of checking involved. Every pair of voices must be checked to ensure there are no parallel fifths and no parallel octaves. That is twelve checks for starters. Three more checks to make sure the bass part is consonant with each of the upper parts. There are many more, checking how the melody moves in each part, deciding which note to double, and so on.
There is no shortcut in voice leading, it is all hard graft.
The principles of voice leading are set out below together with a method for writing it. They are followed by a detailed look at voice leading and the issues involved in writing voice leading in which the root moves by repeat, by fifth, by step and then by third.
The principles of voice leading are:
The rule of the shortest way is used to write voice leading:
Audio: voice leading by repeat (0:02)
voice leading by repeat plays repeat chords. The box in the voice leading by repeat figure shows the score.
A repeat chord is a deceptively simple place to start writing voice leading. It illustrates a lot of the detailed features of voice leading and is a helpful way to untangle the rules.
The first pair of chords is I-I, a repeat chord. Both chords are in root position and are identical. The progression contains what look suspiciously like parallel fifths and octaves, which are prohibited in voice leading. However, the notion of relative motion only applies to parts that move up or down in pitch, it does not apply when all the parts are stationary. A repeat chord does not contain parallel octaves and fifths, it contains stationary octaves and fifths. None of the notes move, the chord does not move, and there is no motion, whether parallel, direct, oblique or contrary.
The second pair of chords is I-Ib, the I is in root position and the Ib is in first inversion. The progression contains two different consecutive notes in the bass, C-E, and two different notes in the tenor, C-G. Whenever two consecutive notes in a voice differ, there is motion and the rules of voice leading apply. When the notes are in the upper voices the nature of the triad does not change, when they are in the bass part the triad becomes inverted. A progression from a root position triad to a first inversion triad is perfectly OK, as is the reverse, from first inversion to root position. A second inversion triad is not allowed in functional harmony because it creates a dissonant interval, the fourth, between the bass and one of the upper parts. There is one exception, when a second inversion triad is used in a special type of cadence known as a 6-4 cadence.
The third pair of chords is Ib-I. The I is voiced differently to the preceding tonic triads. This is because the two upper voices have already been reduced to a state of terminal boredom by repeating the same note three times in succession. The melodies in each of the SA parts are singable, of course, but the notes are not ordered or varied, which breaches the principle of a well-formed melody. It is usual to limit the number of repeat notes in a part to a maximum of three. You cannot have everything in functional harmony, though. Some principles are in conflict with each other. In this instance the victim is step motion, it is not possible to move a note by step in a repeat triad, it has to leap.
Audio: voice leading by fifth (0:03)
voice leading by fifth shows voice leading chords in which the root moves by fifth. The box in the voice leading by fifth figure shows the score.
Voice leading by fifth is the most popular chord progression in harmony. It is worth spending some time looking at how to write it in functional harmony.
The first pair of chords is I-V and features root progression up a fifth. The chord change is CEGC-GDGB. This is how it was written:
The second pair of chords is V-I and features root progression down a fifth. This V-I is simply the previous I-V reversed. In principle, any chord progression can be reversed as long as it contains well-formed melodies, consonant intervals between the bass and upper parts and no parallel fifths or octaves. This significantly simplifies the task of writing voice leading. The second bar thus forms a symmetrical I-V-I chord progression. The only thing to watch out for in V-I is the leading note, B, the seventh degree of the scale. This usually resolves upwards by step to the tonic C. Usually, but not always, because it can occasionally resolve downwards, especially when it is in the inner voices.
The third pair of chords is I-IV and features root progression up a fourth. Using the same approach for I-IV as for I-V, but without the detail, results in the following:
The fourth and final pair of chords is IV-I. The I is repeated so that the I-IV-I progression forms another symmetrical set of chord changes.
Audio: voice leading by step (0:03)
voice leading by step shows voice leading chords in which the root moves by step. The box in the voice leading by step figure shows the score.
Voice leading by step provides the strongest contrast in a chord progression. Two triads a step apart share no notes in common and contain six out of the seven notes in the scale.
The first three chords form a I-ii-I progression featuring root motion by step up then down. The score illustrates a common solution to voice leading by step which is to move all three upper voices in contrary motion to the bass. Another popular solution is to move one of the SAT voices in parallel thirds with the bass whilst the two remaining SAT voices move in contrary motion. This is a good option when the leading note is present in one of the chords as the leading note usually resolves upwards by step to the tonic. For example, the V-vi chord progression G-Am contains the leading note B and resolves GBGD-ACEC.
The last three chords form a V-IV-V progression featuring root motion by step down then up. Although this is valid voice leading, and step motion provides the strongest contrast of all, some commentators have struggled to justify this motion on theoretical grounds. Even the simple IV-V causes some functional head scratching, while V-IV is even more problematic given that the usual function of the dominant V is to lead back home to the tonic I. In practice, when voice leading by step between IV and V occurs, it is usually by step up, I-IV-V-I, rather than step down I-V-IV-I.
One other point worth mentioning here concerns progress to the diminished triad viio. Whether by step or by leap, this progression requires some care. A diminished triad has to be in first inversion to avoid the tritone which would occur if the bass part was in root position. The tritone resolves inward if it is a diminished fifth, for example BF-CE, and outward if it is an augmented fourth, for example, FB-EC. The third above the root of the chord is always doubled. For example, the progression viiob-I, Bdim-C, resolves DDFB-CGEC.
Audio: voice leading by third (0:03)
voice leading by third shows voice leading chords in which the root moves by third. The box in the voice leading by third figure shows the score.
The three chords form a I-iii-I progression featuring root motion by third up then down.
Voice leading by third provides the weakest contrast in a chord progression. Two triads a third apart share two notes in common. There is only one note that differs.
One solution is to put the note that differs in the soprano part, where its effect will be most marked, and to move the part in contrary motion to the bass. This is shown in the score, the bass leaps up a third from C to E and the soprano steps down gracefully from C to B. This provides a pleasant contrast between the two outer voices as they move in contrary motion.
The problem is what to do with the inner voices.
One option is to keep the common tones in the alto and tenor and let them move by oblique motion.
Another option is to retain one of the common notes in one of the inner voices whilst moving the other voice in parallel thirds with the bass. This is the solution shown in the score. The common note is in the tenor voice and the alto moves in parallel thirds with the bass.
A further option is to use an incomplete triad. In functional harmony, a complete triad is preferred to an incomplete triad. However, an incomplete triad is not banned, and it is a handy alternative whenever you get stuck. An incomplete triad must contain the root and third which means that the fifth is the note that is usually omitted (there most definitely is no power chord in functional harmony). A tripled note is not allowed in an incomplete chord except at the end of a section of music as part of a cadence.
Voice leading by third, although uncommon in functional harmony, can be used as an alternative to moving by a single fifth, for example, I-vi-IV-V-I instead of I-IV-V-I and I-iii-V-I instead of I-V-I.
