For the Ornette Coleman album see Free Jazz: A Collective Improvisation.Free jazz is an approach to jazz music that was first developed in the 1950s and 1960s. Though the music of free jazz composers varied widely, a common feature was dissatisfaction with the limitations of bebop, hard bop, and modal jazz that had developed in the 1940s and 1950s. Free jazz musicians attempted to alter, extend, or break down jazz convention, often by discarding fixed chord changes or tempos. While usually considered avant-garde, free jazz has also been described as an attempt to return jazz to its primitive, often religious, roots and emphasis on collective improvisation.As its name implies, free jazz cannot be defined more than loosely, as many musicians draw on free jazz concepts and idioms, and it was never completely distinct as a genre. Many free jazz musicians, notably Pharoah Sanders and John Coltrane, used harsh overblowing or other techniques to elicit unconventional sounds from their instruments, or played unusual instruments. Free jazz musicians created a progressive musical language which drew on earlier styles of jazz such as Dixieland jazz and African music. Typically this kind of music is played by small groups of musicians. The music often swings but without regular meter, and there are frequent accelerandi and ritardandi.Free jazz is strongly associated with the 1950s innovations of Ornette Coleman and Cecil Taylor and the later works of saxophonist John Coltrane. Other important pioneers include Charles Mingus, Eric Dolphy, Albert Ayler, Archie Shepp, Joe Maneri and Sun Ra. Coleman pioneered many techniques typical of free jazz, most notably his rejection of pre-written chord changes, believing instead that freely improvised melodic lines should serve as the basis for harmonic progression in his compositions. Some of bassist Charles Mingus's work was also important in establishing free jazz. Of particular note are his early Atlantic albums, such as The Clown, Tijuana Moods, and most notably Pithecanthropus Erectus, the title song of which contained one section that was freely improvised in a style unrelated to the song's melody or chordal structure. Although today ""free jazz"" is the generally used term, many other terms were used to describe the loosely defined movement, including ""avant-garde"", ""energy music"" and ""The New Thing"". During its early and mid-60s heyday, much free jazz was released by established labels such as Prestige, Blue Note, and Impulse, as well as independents such as ESP Disk and BYG Actuel.Keith Johnson of AllMusic describes a ""Modern Creative"" genre, in which ""musicians may incorporate free playing into structured modes -- or play just about anything."" Johnson includes John Zorn, Henry Kaiser, Eugene Chadbourne, Tim Berne, Bill Frisell, Steve Lacy, Cecil Taylor, Ornette Coleman, and Ray Anderson in this genre, which continues ""the tradition of the '50s to '60s free-jazz mode"".