Answer:
The movement from the single-melody chant, or monophony, to multiple melodies sung or played at the same time, or polyphony, was largely born out of a need to use multiple voices from the Greek times. The first unison sung was the octave, and this type of singing came out of a need for boys and men to sing the same melody. This process is known to ancient Greece as magadizing. I do not think some radical monk started the movement, but rather that it was a gradual process in which a group of people realized that it sounded pleasant to have multiple voices sing different melodies at the same time. The move to polyphony was a giant step in music because it opened up many possibilities about what can be done with music, as opposed to the traditional monophonic music, by adding layers of sound and depth to the music.
Explanation: