", ▁however , ▁Carter ▁creates ▁a ▁gravit ational ▁pull ▁toward ▁a ▁central ▁tempo ▁of ▁ ▁= ▁ 9 6 , ▁the ▁" imper cept ible ▁heart ▁beat " ▁of ▁the ▁quart et , ▁which ▁generally ▁remains ▁hidden . ▁Because ▁a ▁sense ▁of ▁tempo ▁re lies ▁on ▁a ▁clearly ▁established ▁regular ▁pul se , ▁and ▁Carter ▁only ▁creates ▁such ▁un ambigu ous ▁ ▁pass ages ▁during ▁metric ▁mod ulations , ▁it ▁is ▁at ▁those ▁trans itions ▁where ▁these ▁rh yth mic ▁ident ities ▁become ▁clear . ▁ ▁Disc ography ▁Carter , ▁Elli ott . ▁Chamber ▁Music ▁[ String ▁Quart et ▁No . ▁ 5 , ▁ 9 0 + , ▁Son ata ▁for ▁C ello ▁and ▁P iano , ▁Fig ment , ▁Du o ▁for ▁Vi olin ▁and ▁P iano , ▁and ▁Fragment ▁for ▁string ▁quart et ]. ▁Urs ula ▁O pp ens ▁( p iano ); ▁Ar d itt i ▁String ▁Quart et . ▁CD ▁audio ▁disc . ▁Mont a igne ▁MO ▁ 7 8 2 0 9 1 . ▁France : ▁A uv id is , ▁ 1 9 9 8 . ▁Carter , ▁Elli ott . ▁The ▁Complete ▁String ▁Quart ets ▁ 1 – 5 . ▁Pacific a ▁Quart et . ▁ 3 ▁CD ▁audio ▁disc s . ▁N ax os ▁ 8 . 5 0 3 2 2 6 ▁( 1 8 5 5 9 3 6 2 ; ▁ 8 5 5 9 3 6 3 ; ▁ 8 5 5 9 6 1 4 ). ▁Franklin , ▁T