Who was a leading figure in the avant-garde jazz movement of the 1960s?

The leading figure in the avant-garde jazz movement of the 1960s was Ornette Coleman. His work was pioneering in the sense that he introduced a new approach to harmony, melody, and improvisation that significantly departed from the traditional structures that characterized earlier jazz styles. Coltrane was indeed a transformative figure in jazz during this period and ventured into avant-garde territory, particularly with works like "A Love Supreme," but it was Coleman who is often credited with defining avant-garde jazz through his innovative album "The Shape of Jazz to Come." This album and others showcased free jazz and the idea of improvisation without predetermined chord changes, which laid the groundwork for many subsequent jazz musicians.

Mingus and Evans, while incredibly influential in their own right, were more associated with other styles within jazz. Mingus was known for his complex arrangements and incorporation of social themes in music, while Evans made significant contributions to modal jazz and piano trio formats. Understanding Coleman's role helps to clarify the development of jazz in the 1960s and the transition towards more experimental forms that sought to break conventional boundaries.