Premise: The term "four-part harmony" refers to music written for four voices or for some other musical medium—four musical instruments or a single keyboard instrument, for example—where the various musical parts can give a different note for each chord of the music.
Hypothesis: The term "four-part harmony" refers to music written for four voices or for some other musical medium—where the various musical parts can give a different note for each chord of the music. Music is a very popular medium for communication among humans.