aleatory music

Method of composition practised by post-war avant-garde composers in which the performer or conductor chooses the order of succession of the composed pieces. Examples of aleatory music include Pierre Boulez's Piano Sonata No 3 (1956–57), Earle Brown's Available Forms I (1961), and Stockhausen's Momente/Moments (1961–72). Another term for aleatory music is ‘mobile form’.

Aleatory music is distantly related to the 18th-century ‘musical dice game’ and to the freely assembled music for silent movies using theme catalogues by Giuseppe Becce and others. The use by John Cage of dice and the I Ching differs in that it intervenes in the actual process of composition.