1 8 2 . ▁However ▁there ▁was ▁evidence ▁of ▁musical ▁cre ativity ▁there ▁from ▁the ▁early ▁tw elf th ▁century . ▁▁ ▁Lé on in ' s ▁work ▁was ▁distinguished ▁by ▁two ▁distinct ive ▁organ um ▁styles , ▁pur um ▁and ▁disc ant us . ▁This ▁early ▁poly ph onic ▁org ana ▁was ▁still ▁firm ly ▁based ▁on ▁Greg or ian ▁chant , ▁to ▁which ▁a ▁second ▁voice ▁was ▁added . ▁The ▁chant ▁was ▁called ▁the ▁ten or ▁( c ant us ▁firm us ▁or ▁vo x ▁princip alis ), ▁which ▁literally ▁“ holds ” ▁( Lat in : ▁ten ere ) ▁the ▁mel ody . ▁The ▁ten or ▁is ▁based ▁on ▁an ▁existing ▁pla ins ong ▁mel ody ▁from ▁the ▁lit urg ical ▁re per toire ▁( such ▁as ▁the ▁Alle lu ia , ▁Ver se ▁or ▁Grad ual , ▁from ▁the ▁Mass , ▁or ▁a ▁Res p ons ory ▁or ▁Ben edic am us ▁from ▁the ▁Office ). ▁This ▁quot ation ▁of ▁plain chant ▁mel ody ▁is ▁a ▁defining ▁characteristic ▁of ▁th ir teenth ▁century ▁musical ▁gen res . ▁In ▁organ um ▁pur um ▁the ▁ten or ▁part ▁was ▁drawn ▁out ▁into ▁long ▁ped al ▁points , ▁while ▁the ▁upper ▁part ▁or ▁du pl um ▁contrast ed ▁with ▁it ▁in ▁a ▁much ▁fre er ▁rh ythm , ▁consisting ▁of ▁mel isms ▁( mel ism atic ▁or ▁several ▁notes ▁per ▁sy ll able , ▁compared ▁to ▁sy ll ab ic , ▁a ▁single ▁note ▁per ▁sy ll able ). ▁In ▁the ▁second