(AACM), cooperative organization of musicians, including several major figures of free jazz. The musical innovations of the AACM members became important influences on the idiom's development.

Of the approximately three dozen Chicago musicians who formed the AACM, most had played in an early 1960s rehearsal band led by pianist-teacher Muhal Richard Abrams that had experimented with polytonal and atonal jazz and used then-new free jazz techniques of improvisation and composition. They founded the AACM to produce their own concerts in 1965; however, a shared spirit of musical exploration quickly came to dominate their ventures. AACM members were expected to be adept at composition and improvisation and to present concerts that included only original music. Abrams was the organization's leader in its early years; the Art Ensemble of Chicago, drummer Steve McCall, trumpeter Leo Smith, and saxophonists Fred Anderson, Anthony Braxton, and Henry Threadgill were among its other notable performers and composers.

Also in the 1960s the AACM began a school to provide free musical instruction to inner-city youth. After the Art Ensemble and Braxton's ensemble began appearing in Europe in 1969, the AACM became internationally known. As older members moved away from Chicago, AACM school graduates—including woodwind virtuoso Douglas Ewart and trombonist George Lewis—took their places. The AACM musicians' discoveries in terms of sound colour, fluid rhythms, structure, and free jazz lyricism continued to be influential in the 1990s.