The Monophonic Heresy was, according to A Short Guide to Catholic Church History, a heretical belief that the Heavenly Host sings with one voice and not with many hierarchically arranged voices. Sector of Rheims, known as "the Flawless Thinker," was a skeptic of this heresy (Saint Fidgeta and Other Parodies, 60).
The name stems from monophonic: having a single channel or monaural.
|5. A Short Guide to Catholic Church History|