Influenced by John Cage's principles of indeterminacy, Cornelius Cardew (Britain, 1936) organized monumental works that defied the logic of composition, such as Great Learning (1971), a four-hour composition, based on the eponymous Confucian classic, scored for non-singers producing random vocal noises or Treatise (1967), whose score is a 193-page manual of instructions.

AMM was one of the early ensembles of live electronic music, first documented in the free improvised pieces of AMMusic (1966), featuring Cornelius Cardew on piano and cello, Lou Gare on tenor saxophone and violin, Eddie Prevost on percussion, Keith Rowe on guitar, Lawrence Sheaff on cello, accordion and clarinet (and three of them also on transistor radio).

Another ensemble of live electronic music, Musica Elettronica Viva, formed in 1966 in Rome by Frederic Rzewski, Alvin Curran and Richard Teitelbaum, recorded Rzewski's monumental Spacecraft (1967).

Italy was also the land of Gruppo di Improvvisazione Nuova Consonanza, formed by composer Franco Evangelisti and featuring the young Ennio Morricone, another ensemble devoted to group improvisation in a classical-music setting.

The aesthetics of Frederic Rzewski (1938) bridged compositional indeterminacy and jazz improvisation, for example in the lively agit-prop variations of The People United Will Never Be Defeated (1975), a stochastic exercise on a touching Chilean theme, and in the colossal, seven-hour The Road (2002), a summation of all possible piano techniques, including mouth noises produced by the performer.

Robert Ashley (1930), active between Ann Arbor (site of the "ONCE" festival) and the Mills College, coined a new form of opera, that relied on layers of trivial verbal events to create meaning. It was more "sound verite`" than "stream of consciousness", because its source was the accidents of life, not the organic working of a particular psyche. Ashley's operas are garbage cans full of debris, but "revealing" debris, debris that contain clues about people's lives. Melancholy conversational operas for voice and electronics such as Automatic Writing (1979) and Perfect Lives (1983) seems obsessive analyses of urban alienation. The music is a sophisticated flow of unassuming melodies that borrow from centuries of musical repertory. The atmosphere retains something of the angst of expressionist drama, but the prevailing feeling of spleen and resignation are almost antithetic to the "shout" of expressionism.

A similar project was attempted by Ashley's collaborator Robert "Gene Tyranny" Sheff (USA, 1945) with the "cantata" A Letter From Home (1976) for voice and electronics. Sheff mostly experimented with new forms of composition. For example, How To Discover Music In The Sounds Of Your Daily Life (1992) electronically processed found sounds to create "transforms" that were then used to compose orchestral pieces. The Invention of Memory (2003) for baritone, string ensemble, guitar and piano, was a set of variations on a "reference song" that is subjected to several different methods of processing (similar to the way a past memory is recalled differently over time).

Gordon Mumma (USA, 1935), co-founder of Ann Arbor's ONCE festival with Ashley, crafted the dense and apocalyptic sonic masses of his electro-acoustic sculptures Megaton (1963), a mixture of improvised action-music and tape collage, the pioneering multimedia show Space Theatre (1964), and another angst-ridden experiment with collage and electronics, Dresden Interleaf (1965). The audience is part of the score in Cybersonic Cantilevers (1973) because it "offers" sounds to a machine that regurgitates them according to its own algorithm.

Another ONCE pioneer, Roger Reynolds (USA, 1934), toyed with live electronic music in pieces such as Ping (1969), but mainly composed the five vocal symphonies titled Voicespace (1986) for electronically warped voices.

Gavin Bryars (Britain, 1943) experimented with different styles, notably in Jesus' Blood Never Failed Me Yet (1971), "symphonic" variations obtained by electronically processing a tramp's song, and in the Hommages (1981), aleatory pieces derived from other composer's music.

Other composers influenced by the Fluxus aesthetic included Philip Corner (USA, 1933), who even composed sonatas for pianist cleaning the dirty keys of the keyboard, Jackson Mac Low (USA, 1922), whose instructions to the performers often included notes to "listen" not just to play, Walter Marchetti (Italy, 1931), whose eccentric ideas were documented on La Caccia (1974), Yasunao Tone (Japan, 1935), famous for his "concrete" collages of damaged discs such as Music for Two CD Players (1982), Tom Johnson (USA, 1939), composer of the Four Note Opera (1972), built, literally, around four notes only, Nicolas Collins, with Devil's Music (1985), an electronically-processed collage of random radio sounds, Fast Forward (Britain), whose Simultaneous Music (1992) has a score that consists of instructions to performers who have been forbidden to rehearse together and are forbidden to listen to each other.

Pierre Bastien (France, 1953) built his own mechanical orchestra, an ensemble of musical automata capable of playing traditional instruments, documented on Mecanium (1988) and Pop (2005).

In 2010 Christian Marclay (USA, 1955) created a large-scale installation at the Whitney Museum in which some 50 avantgarde performers (including Joan LaBarbara, Elliott Sharp, Alan Licht, Zeena Parkins) performed according to "scores" that were nothing else than piles of three-dimensional objects, while pianists such as Robin Holcomb improvised based on the "score" of a chalkboard on which the audience was invited to scribble or draw at will. Cage thought that all sounds are music. Marclay expanded that notion to every object: all images are possible notations for music. The interaction between visual and audio realms is pushed to the extreme of recusion: Screem Play (2005) was a 29-minute collage of videos that becomes the score based on which improvisers play music, and that performance becomes in turn the film of which it is the soundtrack. Graffiti Composition (originally conceived in 1996) was recorded by an ensemble of improvisers "conducted" by Elliott Sharp. It is debatable who the author is: Marclay had the idea of posting blank posters around a city; random passers-by scribbled on the posters; Sharp used the posters as the score for the composition; and the performers, using their idiosyncratic languages at the instrument, are the ones who actually turned those meaningless signs into the music of the album.