aleatory music (ā`lēətôr'ē) [Lat. alea=dice game], music in which elements traditionally determined by the composer are determined either by a process of random selection chosen by the composer or by the exercise of choice by the performer(s). At the compositional stage, pitches, durations, dynamics, and so forth are made functions of playing card drawings, dice throwings, or mathematical laws of chance, the latter with the possible aid of a computer. Those elements usually left to the performers' discretion include the order of execution of sections of a work, the possible exclusion of such sections, and subjective interpretation of temporal and spatial pitch relations. Also called "chance music," aleatory music has been produced in abundance since 1945 by several composers, the most notable being John Cage Cage, John, 1912–92, American composer, b. Los Angeles. A leading figure in the musical avant-garde from the late 1930s, he attended Pomona College and later studied with Arnold Schoenberg , Adolph Weiss, and Henry Cowell .
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aleatory music

(from Latin, alea: “dice game”) Any 20th-century music, particularly that of the 1950s and '60s, the composition or performance of which incorporates elements of chance. In aleatory music aspects such as the ordering of a piece's sections, its rhythms, and even its pitches are decided at the moment of performance. When not purely improvising, players follow lists of arbitrary rules or interpreted “graphic” notation that merely suggest the sounds. Charles Ives and Henry Cowell had used such techniques, but John Cage became the principal figure in aleatory; other aleatory composers include Earle Brown (1926–2002), Morton Feldman (1926–87), and Pierre Boulez.