▁This ▁collection ▁of ▁music ▁constit utes ▁the ▁earliest ▁known ▁record ▁of ▁poly phony ▁to ▁have ▁the ▁stability ▁and ▁circul ation ▁achieved ▁earlier ▁by ▁mon oph onic ▁Greg or ian ▁chant . ▁ ▁P é rot in ' s ▁musical ▁forms ▁and ▁style ▁▁▁ ▁Louis ▁VII ▁was ▁succeeded ▁by ▁his ▁son ▁Philip ▁II ▁in ▁ 1 1 7 9 ▁and ▁his ▁reign ▁was ▁marked ▁by ▁integration ▁and ▁revision ▁of ▁the ▁cultural ▁sh ifts ▁that ▁had ▁trans p ired ▁under ▁his ▁father . ▁It ▁was ▁during ▁this ▁time ▁that ▁the ▁compos itions ▁of ▁P é rot in ▁first ▁appeared , ▁and ▁a ▁shift ▁towards ▁a ▁more ▁pre domin ant ▁disc ant us ▁style . ▁P é rot in ▁is ▁best ▁known ▁for ▁his ▁composition ▁of ▁both ▁lit urg ical ▁org ana ▁and ▁non - lit urg ical ▁conduct i ▁in ▁which ▁the ▁voices ▁move ▁note ▁on ▁note . ▁He ▁pione ered ▁the ▁styles ▁of ▁organ um ▁tri pl um ▁and ▁organ um ▁quad ru pl um ▁( three ▁and ▁four - part ▁poly phony ) ▁and ▁his ▁V ider unt ▁om nes ▁and ▁S eder unt ▁princip es , ▁Grad uals ▁for ▁Christmas ▁and ▁the ▁fe ast ▁of ▁St ▁Stephen ' s ▁Day ▁( Dec ember ▁ 2 6 ) ▁respectively ▁are ▁among ▁only ▁a ▁few ▁org ana ▁quad ru pla ▁known , ▁early ▁poly phony ▁having ▁been ▁restricted ▁to ▁two - part ▁compos itions . ▁With ▁the ▁addition ▁of ▁further ▁parts , ▁the ▁compos itions ▁became ▁known ▁as ▁mot ets , ▁the ▁most ▁important