) ▁of ▁a ▁chant ▁at ▁intervals ▁of ▁a ▁fourth ▁or ▁fifth , ▁above ▁or ▁below . ▁This ▁school ▁also ▁marked ▁a ▁transition ▁from ▁music ▁that ▁was ▁essentially ▁performance ▁to ▁a ▁less ▁e ph em eral ▁entity ▁that ▁was ▁committed ▁to ▁par ch ment , ▁preserved ▁and ▁transm itted ▁to ▁history . ▁It ▁is ▁also ▁the ▁beginning ▁of ▁the ▁idea ▁of ▁compos ers ▁and ▁compos itions , ▁the ▁introduction ▁of ▁more ▁than ▁two ▁voices ▁and ▁the ▁treatment ▁of ▁vern ac ular ▁texts . ▁For ▁the ▁first ▁time , ▁rh ythm ▁became ▁as ▁important ▁as ▁pitch , ▁to ▁the ▁extent ▁that ▁the ▁music ▁of ▁this ▁era ▁came ▁to ▁be ▁known ▁as ▁musica ▁mens ur abil is ▁( music ▁that ▁can ▁be ▁measured ). ▁These ▁develop ments ▁and ▁the ▁notation ▁that ▁evol ved ▁laid ▁the ▁found ations ▁of ▁musical ▁practice ▁for ▁centuries . ▁The ▁surv iving ▁manuscript s ▁from ▁the ▁th ir teenth ▁century ▁together ▁with ▁the ▁contempor aneous ▁treat ises ▁on ▁musical ▁theory ▁const itute ▁the ▁musical ▁era ▁of ▁ar s ▁anti qua . ▁The ▁Notre ▁D ame ▁re pert ory ▁spread ▁throughout ▁Europe . ▁In ▁Paris ▁poly phony ▁was ▁being ▁performed ▁in ▁the ▁late ▁ 1 1 9 0 s ▁but ▁later ▁sources ▁imply ▁that ▁some ▁of ▁the ▁compos itions ▁date ▁back ▁as ▁far ▁as ▁the ▁ 1 1 6 0 s . ▁Although ▁often ▁linked ▁to ▁the ▁construction ▁of ▁the ▁c athedral ▁itself , ▁construction ▁comm enced ▁in ▁ 1 1 6 3 ▁and ▁the ▁alt ar ▁consec r ated ▁in ▁ 1