us ▁sets ▁a ▁rh ym ed ▁Latin ▁poem ▁called ▁a ▁sequence ▁to ▁a ▁repeated ▁mel ody , ▁much ▁like ▁a ▁contemporary ▁h ymn .) ▁By ▁tradition , ▁the ▁four - part ▁pieces ▁of ▁the ▁Notre ▁D ame ▁school ▁have ▁been ▁attributed ▁to ▁P é rot in , ▁leaving ▁the ▁two - part ▁pieces ▁to ▁Lé on in . ▁The ▁former ▁include ▁the ▁three - part ▁conduct us ▁Salv ator ▁h od ie . ▁The ▁latter ▁is ▁placed ▁in ▁the ▁Mass ▁for ▁the ▁Circ um c ision ▁in ▁a ▁ 1 3 th ▁century ▁French ▁manuscript . ▁Of ▁these , ▁the ▁best ▁known ▁works ▁are ▁his ▁V ider unt ▁om nes ▁and ▁S eder unt ▁princip es . ▁These ▁have ▁been ▁described ▁as ▁representing ▁the ▁peak ▁of ▁musical ▁development ▁of ▁the ▁time . ▁ ▁Most ▁of ▁P é rot in ' s ▁works ▁are ▁in ▁poly ph onic ▁form ▁of ▁disc ant , ▁including ▁the ▁quad ru pla ▁and ▁tri pla . ▁Here ▁the ▁upper ▁voices ▁move ▁in ▁disc ant , ▁as ▁rh yth mic ▁counter point ▁above ▁the ▁sust ained ▁ten or ▁notes . ▁This ▁is ▁consistent ▁with ▁An onymous ▁IV ' s ▁description ▁of ▁him ▁as ▁optim us ▁disc ant or . ▁However , ▁like ▁Lé on in , ▁he ▁is ▁likely ▁to ▁have ▁composed ▁in ▁every ▁musical ▁genre ▁and ▁style ▁known ▁to ▁Notre ▁D ame ▁poly phony . ▁ ▁P é rot in ' s ▁dates ▁of ▁activity ▁have ▁been ▁approxim ated ▁from ▁some ▁late ▁ 1 2 th ▁century ▁ed