 His work with electronic music and its utter fixity led him to explore modes of instrumental and vocal music in which performers ' individual capabilities and the circumstances of a particular performance ( e.g. , hall acoustics ) may determine certain aspects of a composition . He called this " variable form " ( Wörner 1973 , 101 – 105 ) . In other cases , a work may be presented from a number of different perspectives . In Zyklus ( 1959 ) , for example , he began using graphic notation for instrumental music . The score is written so that the performance can start on any page , and it may be read upside down , or from right to left , as the performer chooses ( Stockhausen Texte , 2 , 73 – 100 ) . Still other works permit different routes through the constituent parts . Stockhausen called both of these possibilities " polyvalent form " ( Stockhausen Texte , 1 : 241 – 51 ) , which may be either open form ( essentially incomplete , pointing beyond its frame ) , as with Klavierstück XI ( 1956 ) , or " closed form " ( complete and self @-@ contained ) as with Momente ( 1962 – 64 / 69 ) ( Kaletha 2004 , 97 – 98 ) . 
