Definition: A style of music dating from the 1950s and 60s. The name most likely comes from an Ornette Coleman album entitled Free Jazz: A Collective Improvisation, released in 1961. Free jazz usually involved the abandonment of chord changes, song structure, and in some cases, conventional tone and technique. Although it was often dismissed by listeners, it has proven to be very influential on today’s jazz.
Examples:
Ornette Coleman's The Shape of Jazz to Come, included in my list of Ten Classic Jazz Recordings is an example of the beginnings of free jazz.
