During the earlier medieval period, the vocal music from the liturgical genre, predominantly Gregorian chant, was monophonic, using a single, unaccompanied vocal melody line. Polyphonic vocal genres, which used multiple independent vocal melodies, began to develop <answer>during the high medieval era</answer>, becoming prevalent by the later 13th and early 14th century.
When did the Polyphonic vocal genre begin to develop?
during the high medieval era