Editing Gradual (section)

==Polyphonic settings==
Graduals were among the parts of the Mass most frequently composed as [[organum|organa]], including both the [[St. Martial School]] and the [[Notre Dame School]]. Ordinarily the parts that were sung by the soloist (the beginning of the respond and the verse) are the only parts so set, while the choral parts continued to be performed in plainsong. In 1198, [[Odo de Sully]], [[Bishop of Paris]], authorized [[polyphony|polyphonic]] performances of Graduals, including [[Pérotin]]'s famous four-part [[organum|organa]], ''[[Sederunt principes]]'' for [[St. Stephen]]'s Day and ''[[Viderunt omnes]]'' for [[Christmas]].{{ref|ref06}}