Presumably French medieval composer Pérotin (ca. 1160-ca. 1230) was the principal composer of sacred organum of more than two voices and the figure who raised the so-called Notre Dame School to its artistic zenith, though it hasn't been proven that he ever served at Notre Dame Cathedral. Known by attributions in manuscripts and an account from thirteenth century English theorist Anonymous IV, Pérotin is incontrovertibly regarded as author of about 16 compositions ranging from three to four voices, with a few others seen as belonging to his specific school: the Organa Viderunt omnes, Sederunt principes, and Alleluia nativitas are among his most famous works.