How do “voice-leading”, “part-writing”, “polyphony” and “counterpoint” differ?

Question

What are the differences in meaning and usage between “voice-leading”, “part-writing”, “polyphony” and “counterpoint”?

According to Wikipedia:

• 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 principles of common-practice harmony and counterpoint.”.
• Part-writing redirects to Voice-leading, yet there it says that “Voice leading practices can be codified into rules for pedagogical purposes. In these settings, ‘voice leading’ is often synonymous with ‘part writing,’ …” — that suggests that it is not always synonymous!
• Counterpoint is “the relationship between voices that are harmonically interdependent (polyphony) yet independent in rhythm and contour.”
• Polyphony is a “musical texture … that consists of two or more simultaneous lines of independent melody”.

The currently accepted answer to another question clarifies that counterpoint is polyphony obeying certain rules, so the main issue is how “voice-leading” and “part-writing” fit in. A summary in one place of how all four terms are used, in different contexts if necessary, would be helpful.

Answer 1

Voice-leading is the set of rules for writing parts; part-writing is synonymous. These rules are descriptive procedures based on the last thousand years of observing musical practice.

Counterpoint is a slightly more general term enclosing the voice-leading rules and some stuff about style.

Polyphony is the practice of thinking of music in terms of combinations of melodies rather than as succession of chords.

All these terms are rather broad; a single piece of music may be written polyphonically with differing "rules" pertaining to the succession of harmonies.

Answer 2

Voice-leading and part-writing are generally the same. Voice-leading generally describes how separate parts (=voices) are supposed move relative to each other. Examples of rules are that the leading tone should always solve, if you're writing for four voices, which note of the chord can be doubled, etc.

Counterpoint is a practice that falls under voice-leading. When practicing counterpoint, you generally don't really look at how you want the melodies to form a dynamic harmony, but you're rather focussing on how to create two (or more) melodies that do work and cooperate together, but also have strong independent identities.

To round this all up, counterpoint is a way of polyphonic writing (= having multiple melodies which all have a strong independent identity. They usually all have each different melodical and rhythmic lines) and voice-leading or part-writing is generally the theory of how these melodies should move relative to each other.

Answer 3

Polyphony and counterpoint:

you can write a counterpoint voice leading without respecting the traditional c.p. rules. The main point is that in this organisation of different parts the voices are each one emanzipated of the other voices, fully indepedent but also interdependent by using similar material, copying motifs or imitating.

Polyphony and homophony:

The real opposite of polyphonic is not unisono or a single voice. It is a homophonic setting, where to a given melody the other voices are less or more homophonic accompaning in chords and harmony the main tune. That means there is no great deviation in the rhythme, the voices are led in the same rhythm as the main tune, note by note filling the chord notes to complete the harmony. Church chorals are mainly homophone settings, while the chorals by Bach can be quite polyphonic as described above. Examples of polyhony are the canon and the fuge (for nearer explanation look up there).

Voice leading is concerning the rules for the different voices, implying rules of ounterpoint and rules for melodic progression, as well as chord progressions. It can be homophone (vertical based) or polyhonal (linear based). There are aspects of singabilty and also balanced intervals, to have a fine and interesting result.

Parts are the simple voices copied from the score for the single instruments or choir voices. They can be homophone or polyphonic or even unisono.

Answer 4

'Polyphony' describes music that combines two or more melodic lines. Not just melody and block chords. (Though even the most monophonic piece may well have some polyphonic interest between melody and bass line. Things are rarely absolute in the music world.)

'Counterpoint' is another word referring to the same thing.

And 'Part-writing' is what you do to get counterpoint.

'Voice leading' is a subset of 'Part Writing' concerned with how one note moves to the next, in the same voice. You could conceivably have good voice leading - each line following a nicely melodic contour with no ugly jumps - but terrible part writing - the combination of voices not making musical sense. This actually happens quite often in elementary attempts at counterpoint. The student writes nice lines for each voice but forgets to make them fit together well!