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 very melodious to listen
( z1 melodious :domain ( z2 harmony :mod ( z3 part :quant 4 ) ) :degree ( z4 very ) :condition ( z5 listen ) )