Avant-garde jazz

Avant-garde jazz (also known as avant-jazz) is a style of music and improvisation that combines avant-garde art music and composition with jazz. Avant-jazz often sounds very similar to free jazz, but differs in that, despite its distinct departure from traditional harmony, it has a predetermined structure over which improvisation may take place. This structure may be composed note for note in advance, partially or even completely.

Source : http://en.wikipedia.org/wiki/Avant-garde_jazz