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.
Four-part harmony is a part of contemporary music
( z1 harmony :part-of ( z2 music :mod ( z3 contemporary ) ) :mod ( z4 part :quant 4 ) )