Voice leading – free music theory course

A chord progression isn't a series of blocks: it's a set of melodic lines (“voices”) moving together. Classical harmony thinks in four voices — soprano, alto, tenor, bass — like a choir. At the piano they are often split this way: soprano and alto in the right hand, tenor and bass in the left.

Ranges and spacing

Soprano: middle C → high G; alto: G below middle C → D; tenor: C an octave below middle C → G; bass: low E → middle C (roughly).
No more than an octave between soprano and alto, or between alto and tenor (the bass may be further away).
Voices don't cross.

Principles of motion

Keep common tones in the same voice.
Take the shortest path: inner voices move by step or small leaps.
The leading tone rises to the tonic (at least in the top voice).
The seventh falls by step.
Favour contrary motion between bass and soprano.
Prefer doubling the root; never double the leading tone.

The most famous prohibition: parallel fifths and octaves

Two voices forming a perfect fifth (or an octave) that move in the same direction to another fifth (or octave) produce parallel (consecutive) fifths or octaves. The two voices fuse and lose their independence: the texture thins out. Compare:

M:4/4
L:1/4
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
K:C
[V:RH] "F"[FA]2 "G"[GB]2 | "F"[FA]2 "G"[DG]2 |]
[V:LH] "_wrong"[F,C]2 [G,D]2 | "_right"[F,C]2 [G,B,]2 |]

Bar 1: every voice moves up a whole tone. F–C becomes G–D (parallel fifths between bass and tenor) and F–F becomes G–G (parallel octaves). Bar 2: the three upper voices move down to the nearest notes of the G chord, in contrary motion to the bass. It sounds better, and it's correct.

Resolving the dominant

In V7 → I, the leading tone rises, the seventh falls, the fifth often falls to the tonic. If V7 is complete, the following tonic chord is often incomplete (tripled root, no fifth): that's perfectly correct.

M:4/4
L:1/4
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
K:C
[V:RH] "C"[Ec]2 "F"[Fc]2 | "G7"[FB]2 "C"[Ec]2 |]
[V:LH] [C,G,]2 [F,A,]2 | [G,D]2 [C,C]2 |]

How to check? For each pair of voices (6 pairs in four parts), note the interval on each chord. If two perfect fifths or two octaves follow each other with both voices moving the same way: fix it.

These rules don't apply everywhere: parallel fifths are the signature of rock (“power chords”), of Debussy and of many world musics. These are rules of style — that of classical tonal music — but they teach you to write independent lines, which is useful in every style.