▁instances ▁of ▁the ▁use ▁of ▁rh yth mic ▁proport ions ▁to ▁govern ▁the ▁structure ▁of ▁individual ▁movements ▁and / or ▁whole ▁works . ▁The ▁proportion ▁is ▁ 4 , ▁ 7 , ▁ 2 , ▁ 5 ; ▁ 4 , ▁ 7 , ▁ 2 , ▁ 3 , ▁ 5 ▁and ▁it ▁affect s ▁only ▁the ▁micro structure ▁of ▁the ▁pieces . ▁ ▁Am ores ▁Com posed ▁in ▁early ▁ 1 9 4 3 ▁after ▁C age ▁moved ▁to ▁New ▁York ▁City , ▁as ▁a ▁concert ▁piece . ▁Ch ore ograph ed ▁by ▁Mer ce ▁C unning ham ▁in ▁ 1 9 4 9 . ▁Am ores ▁contains ▁four ▁movements : ▁ ▁Solo ▁for ▁prepared ▁piano ▁ ▁T rio ▁for ▁ 9 ▁tom - t oms ▁and ▁a ▁pod ▁r attle ▁ ▁T rio ▁for ▁ 7 ▁wood ▁blocks ▁ ▁Solo ▁for ▁prepared ▁piano ▁E igh teen ▁notes ▁are ▁prepared ▁using ▁ 9 ▁sc rew s , ▁ 8 ▁bol ts , ▁ 2 ▁n uts ▁and ▁ 3 ▁stri ps ▁of ▁rub ber . ▁Similarly ▁to ▁Bac chan ale , ▁the ▁perform er ▁is ▁instruct ed ▁in ▁the ▁score ▁to ▁" det erm ine ▁position ▁and ▁size ▁of ▁m utes ▁by ▁experiment ". ▁This ▁was ▁one ▁of ▁C age ' s ▁earliest ▁works ▁to ▁use ▁C age ' s ▁rh yth mic ▁proport ions ▁technique . ▁The ▁structure ▁of ▁the ▁second ▁movement , ▁for ▁example , ▁is ▁based ▁ 1 0 - bar ▁units ▁each ▁divided ▁into ▁four ▁sections :