Voice leading

Voice leading is the term used to describe the linear progression of melodic lines (voices) and their interaction with one another to create harmonies, according to the principals of common-practice harmony and counterpoint.

Voice leading practices can be codified into rules for pedagogical purposes. In these settings, "voice leading" is often synonymous with "part writing," and the "rules" are usually applied in exercises in four-part harmonic writing and in 18th-century counterpoint. David Huron has demonstrated that many of the standard pedagogical rules have a basis in perceptual principles.

A more nuanced view of voice leading principles is found in the theories of Heinrich Schenker. Schenkerian analysis examines how the outer voices work together to establish form in common-practice music. See Linear progression for an example from Beethoven's Sonata op. 109.

Rigorous concern for voice leading in all parts is more a feature of common-practice music, although jazz and pop music also demonstrate attention to voice leading to varying degrees:

The score in the following example reproduces the first four measures of Johann Sebastian Bach's Preludium in C major (BWV 846a) from the 1722 keyboard work Well Tempered Keyboard, volume 1. Letter (a) presents the original score while (b) and (c) present reductions (simplified versions) intended to clarify the harmony and implied voice leading, respectively.

In (b), the same measures are presented as consisting in four block chords: the first and the fourth ones are the same, a triad of C major (I); the second is a minor 7th chord on D (II), inverted to show C in the bass; the third is a dominant 7th on G (V), inverted to show B in the bass.

In (c), the four measures are presented as formed of five horizontal parts (voices) identified by the direction of the stems, each consisting in only three notes: from top to bottom, (1) E F — E; (2) C D — C; (3) G A G —; (4) E D — E; (5) C — B C. The four chords result from the fact that not every voice moves at the same time. To see this, look at the highest note of each chord - E, F, F, and E - this corresponds to 1), the second highest note of each chord is C, D, D, and C - corresponding to 2) etc.

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