Music that combines several simultaneous voice-parts of individual design, in contrast to monophonic music, which consists of a single melody, or homophonic music, which combines several voice-parts of similar, rhythmically identical design.  The prefix "poly-" should not be taken literally, since as few as two parts can make perfect polyphony -- better indeed, than six or eight.  Polyphony is largely synonymous with counterpoint, except for a difference of emphasis.

There are numerous theories regarding the "origin of polyphony," but none is more than hypothetical.  Some scholars regard the earliest extant examples of polyphony (c. 900) not as a beginning but as a "first culmination" of a development whose origin, they believe, lies in Oriental and primitive music.