Perotin
Succeeded Leonin at Notre
Dame. He developed organum
from the Leonin style by instilling a greater rhythmic accuracy, and by
making additions and modifications to the "Magnus Liber Organi".
His tenor voices were written in a series of rhythmic motives that were
the precursors of the the rhythmic
modes. He expanded organum to three and four voices. In
addition, his music shows evidence of cannonic imitation.
Perotin was skilled in the art of discant,
being described as "optimus discantor," while Leonin
was called "optimus organista."