▁The ▁dimin utive ▁was ▁pres umably ▁a ▁mark ▁of ▁respect ▁best owed ▁by ▁his ▁colle agues . ▁The ▁title ▁Magn us ▁was ▁a ▁mark ▁of ▁the ▁este em ▁in ▁which ▁he ▁was ▁held , ▁even ▁long ▁after ▁his ▁death . ▁ ▁Work ▁ ▁Notre ▁D ame ▁School ▁▁ ▁The ▁reign ▁of ▁Louis ▁VII ▁( 1 1 3 7 – 1 1 8 0 ) ▁witness ed ▁a ▁period ▁of ▁cultural ▁innov ation , ▁in ▁which ▁appeared ▁the ▁Notre ▁D ame ▁school ▁of ▁musical ▁composition , ▁and ▁the ▁contributions ▁of ▁Lé on in , ▁who ▁prepared ▁two - part ▁ch oral ▁settings ▁( org ana ) ▁for ▁all ▁the ▁major ▁lit urg ical ▁festiv als . ▁This ▁period ▁in ▁musical ▁history ▁has ▁been ▁described ▁as ▁a ▁parad ig m ▁shift ▁of ▁last ing ▁consequence ▁in ▁musical ▁notation ▁and ▁rh yth mic ▁composition , ▁with ▁the ▁development ▁of ▁the ▁organ um , ▁cla us ula , ▁conduct us ▁and ▁mot et . ▁The ▁innov ative ▁nature ▁of ▁the ▁Notre ▁D ame ▁style ▁stands ▁in ▁contrast ▁to ▁its ▁prede cess or , ▁that ▁of ▁the ▁Ab bey ▁of ▁St ▁Mart ial , ▁Lim og es , ▁replacing ▁the ▁mon od ic ▁( mon oph onic ) ▁Greg or ian ▁chant ▁with ▁poly phony ▁( more ▁than ▁one ▁voice ▁singing ▁at ▁a ▁time ). ▁This ▁was ▁the ▁beginning ▁of ▁poly ph onic ▁European ▁church ▁music . ▁ ▁Organ um ▁at ▁its ▁roots ▁involves ▁simple ▁dou bling ▁( organ um ▁du pl um ▁or ▁organ um ▁pur um