diaphony (n.)

1650s, "discord," from Greek diaphonia "dissonance, discord," from diaphonos "discordant," from dia "through; throughout" (see dia-) + phone "voice, sound," from PIE root *bha- (2) "to speak, tell, say." From 1834 in reference to medieval music, "earliest form of polyphony, in which two or more voices proceed in strict parallel at intervals of a fourth, fifth, or octave." Related: Diaphonic.