Voice leading is the way that musical parts (voices) set up and achieve melodic, harmonic and formal goals using pitch and rhythm. Often, a variety of parameters work together to produce different weights of arrival. Such parameters may include "the interaction between chords and lines within harmonic progressions [...], the role of outer-voices counterpoint, the types of melodic motion, the retention of common tones, [and] the treatment of dissonance.”  Monophonic lines also exhibit voice leading.
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:
- “At the surface level, jazz voice-leading conventions seem more relaxed than they are in common-practice music."
- “[Although it’s untrue] that popular music has no voice leading in it, [...] the largest amount of popular music is simply conceived with chords as blocks of information, and melodies are layered on top of the chords."
The score in the following example reproduces the first four measures of Bach's Preludium in C major (BWV 846a) from the Well Tempered Keyboard, volume 1. (a) presents the original score while (b) and (c) present reductions intended to clarify the harmony and 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 every voice does not move 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.
- All musical technique is derived from two basic ingredients: voice leading and the progression of scale degrees [i.e. of harmonic roots]. Of the two, voice leading is the earlier and the more original element.
- The theory of voice leading is to be presented here as a discipline unified in itself; that is, I shall show how […] it everywhere maintains its inner unity.
Schenker indeed did not present the rules of voice leading merely as contrapuntal rules, but showed how they are inseparable from the rules of harmony and how they form one of the most essential aspects of musical composition.[example needed] (See Schenkerian analysis: voice leading).
Common-Practice Conventions and Pedagogy
Although pacing a piece’s various arrivals is the most important result of voice leading, Western musicians have tended to teach voice leading by focusing on connecting adjacent harmonies because that skill is foundational to meeting larger, structural objectives.
On a chord-to-chord level, common-practice conventions dictate that lines should be smooth (by avoiding leaps and retaining common tones) and independent (by avoiding simultaneous movement of all voices in the same direction and parallel perfect intervals). Contrapuntal conventions likewise consider permitted or forbidden melodic intervals in individual parts, intervals between parts, the direction of the movement of the voices with respect to each other, etc. (See Counterpoint for more details on rules, especially in species counterpoint; see also Contrapuntal motion.) Whether dealing with counterpoint or harmony, these conventions emerge not only from a desire to create easy-to-sing parts but also from the constraints of tonal materials and from the objectives behind writing certain textures. In other words, the practical, technical, and aesthetic considerations surrounding voice leading reinforce one another.
Various pedagogues have approached teaching these conventions in different ways. For instance, one of the main conventions of common-practice part-writing is that, between successive harmonies, voices should avoid leaps and retain common tones as much as possible. This principle was commonly discussed among 17th- and 18th-century musicians as a rule of thumb. For example, Rameau taught "one cannot pass from one note to another but by that which is closest."
In the 19th century, as music pedagogy became a more theoretical discipline in some parts of Europe, the 18th-century rule of thumb became codified into a more strict definition. Johann August Dürrneberger coined the term "rule of the shortest way" for it and delineated that:
- For a regular conjunction of chords in the accompaniment, three main principles are generally considered, namely:
- 1. When a chord contains one or more notes that will be reused in the chords immediately following, then these notes should remain, that is retained in the respective parts.
- 2. The parts which do not remain, follow the law of the shortest way (Gesetze des nächsten Weges), that is that each such part names the note of the following chord closest to itself, if no forbidden succession arises from this.
- 3. If no note at all is present in a chord which can be reused in the chord immediately following, one must apply contrary motion according to the law of the shortest way, that is, if the root progresses upwards, the accompanying parts must move downwards, or inversely, if the root progresses downwards, the other parts move upwards and, in both cases, to the note of the following chord closest to them.
Schenker re-conceived the principle as the "rule of melodic fluency":
- If one wants to avoid the dangers produced by larger intervals [...], the best remedy is simply to interrupt the series of leaps — that is, to prevent a second leap from occurring by continuing with a second or an only slightly larger interval after the first leap; or one may change the direction of the second interval altogether; finally both means can be used in combination.
- Such procedures yield a kind of wave-like melodic line which as a whole represents an animated entity, and which, with its ascending and descending curves, appears balanced in all its individual component parts. This kind of line manifests what is called melodic fluency [Fließender Gesang].
Schenker attributed the rule to Cherubini, but Cherubini's conception was more in line with his 18th-century peers, saying only that conjunct movement should be preferred. The concept of Fließender Gesang is a common concept of German counterpoint theory. Modern Schenkerians made the concept of "melodic fluency" an important one in their teaching of voice leading.
Neo-Riemannian theory examines another facet of this principle. That theory decomposes movements from one chord to another into one or several "parsimonious movements" between pitch classes instead of actual pitches (i.e., neglecting octave shifts). Such analysis shows the deeper continuity underneath surface disjunctions, as in the Bach example from BWV 941.
Voice Leading and Common-Practice Harmonic Roles
As the Renaissance gave way to the Baroque era, part writing reflected the increasing stratification of harmonic roles. This differentiation between outer and inner voices was an outgrowth of both tonality and homophony. In this new style, the outer voices took a commanding role in determining the flow of the music and tended to move more often by leaps. Inner voices tended to move stepwise or repeat common tones.
A Schenkerian perspective on these roles shifts the discussion somewhat from "outer and inner" to "upper and bass." Although the outer voices still play the dominant, form-defining role in this view, the leading soprano voice is often seen as a composite line that draws on the voice leadings in each of the upper voices of the imaginary continuo. Approaching harmony from a non-Schenkerian perspective, Dmitri Tymoczko nonetheless also demonstrates such "3+1" voice leading as a feature of tonal writing.
Beyond Common-Practice Conventions
Much music that doesn't follow common-practice part-writing conventions nonetheless often follows larger voice leading principles. For instance, Debussy's Nocturnes and Morton Feldman's The Viola in My Life (pieces as different from each other as they are distinct from common-practice era music) both derive their formal connections from soprano voice leading.
In this sense, the conceit of "part-writing rules" is misleading. Wise pedagogues understand that such rules aren't there to be "broken," but to help students hone their perception and develop judgment about the larger principles.
- Terefenko, Dariusz (2014). Jazz Theory: From Basic to Advanced Study, p.33. Routledge. ISBN 9781135043018.
- Huron, David. "Tone and Voice: A Derivation of the Rules of Voice-leading from Perceptual Principles” Music Perception, Vol. 19, No. 1 (2001) pp. 1-64.
- Schonbrun, Marc (2011). The Everything Music Theory Book, pp.174, 149. Adams Media. ISBN 9781440511820.
- Heinrich Schenker, Counterpoint, vol. I, transl. J. Rothgeb and J. Thym, New York, Schirmer, 1987, p. xxv.
- Schenker (1987), p. xxx.
- Miller, Michael (2005). The Complete Idiot's Guide to Music Theory, p.193. Penguin. ISBN 9781592574377.
- Bartlette, Christopher, and Steven G. Laitz (2010). Graduate Review of Tonal Theory. New York: Oxford University Press, pg 47-50. ISBN 978-0-19-537698-2
- Tymoczko, Dmitri (2011). A Geometry of Tonal Music. New York: Oxford University Press. IBSN 978-0-19-533667-2
- Jean-Philippe Rameau, Traité de L'Harmonie Reduite à ses Principes naturels, Paris, 1722, Book 4, pp. 186-7: On ne peut passer d'une Notte à une autre que par celle qui en est la plus voisine. An even earlier version can be found in Charles Masson, Nouveau traité des regles pour la composition de la musique, Paris, Ballard, 1705, p. 47: Quand on jouë sur la Basse pour accompagner, les Parties superieures pratiquent tous les Accords qui peuvent être faits sans quitter la corde où ils se trouvent; ou bien elles doivent prendre ceux qu'on peut faire avec le moindre intervalle, soit en montant soit en descendant.
- Johann August Dürrnberger, Elementar-Lehrbuch der Harmonie- und Generalbass-Lehre, Linz, 1841, p. 53.
- Anton Bruckner, Vorlesungen über Harmonielehre und Kontrapunkt an der Universität Wien, E. Schwanzara ed., Vienna, 1950, p. 129. See Robert W. Wason, Viennese Harmonic Theory from Albrechtsberger to Schenker and Schoenberg, Ann Arbor, London, UMI Research Press, 1985, p. 70. ISBN 0-8357-1586-8
- Schoenberg, Arnold, Theory of Harmony, trans. Roy E. Carter. Belmont Music Publishers, 1983, 1978 (original quote 1911). Page 39. ISBN 0-520-04944-6. Schoenberg writes: "Thus, the voices will follow (as I once heard Bruckner say) the law of the shortest way".
- Heinrich Schenker, Kontrapunkt, vol. I, 1910, p. 133; Counterpoint, J. Rothgeb and J. Thym transl., New York, Schirmer, 1987, p. 94.
- Luigi Cherubini, Cours de Contrepoint et de Fugue, bilingual ed. French/German, Leipzig and Paris, ca 1835, p. 7. Franz Stoepel, the German translator, used the expression Fließender Gesang to translate mouvement conjoint. See Schenkerian analysis.
- See for instance Johann Philipp Kirnberger, Die Kunst des reinen Satzes in der Musik, vol. II, Berlin, Königsberg, 1776, p. 82.
- Allen Cadwallader and David Gagné, Analysis of Tonal Music, 3d ed., Oxford University Press, 2011, p. 17.
- Richard Cohn, "Neo-Riemannian Operations, Parsimonious Trichords, and their 'Tonnetz' Representations", note 4, writes that the term "parsimony" is used in this context in Ottokar Hostinský, Die Lehre von den musikalischen Klangen, Prag, H. Dominicus, 1879, p. 106. Cohn considers the principe of parsimony to be the same thing as the "law of the shortest way", but this is only partly true.
- Cadwaller, Allan; Gagne, David (2010). Analysis of Tonal Music: A Schenkerian Approach. Oxford University Press. ISBN 978-0199732470.
- Tymoczko, Dmitri (2011). A Geometry of Tonal Music. Oxford University Press. pp. 204–207.
- McAdams, S. and Bregman, A. (1979). "Hearing musical streams", in Computer Music Journal 3(4): 26–44 and in Roads, C. and Strawn, J., eds. (1985). Foundations of Computer Music, p. 658–98. Cambridge, Massachusetts: MIT Press.
- "Voice Leading Overview", Harmony.org.uk.