Perhaps the most controversial movement in the history of jazz came with the advent of free jazz, or "New Thing" as it was later to be called. While elements of free jazz existed within the structure of the music for many years, most notably in the "experiments" of such innovators as Coleman Hawkins, Pee Wee Russell and Lennie Tristano, it wasn't until the mid to late '50s that it emerged as a bona fide style, coming as it did from such pioneers as saxophonist Ornette Coleman and pianist Cecil Taylor.

What these two musicians and others such as John Coltrane, Albert Ayler and aggregates such as the Sun Ra Arkestra and a group called the Revolutionary Ensemble did amounted to a variety of changes in the structure and feel of the music. Among the innovations, when performed with imagination and great musicianship, was dispensing with chord progressions, allowing the music to go in any of a number of directions. Another primary change could be found with rhythm, where "swing" was either redefined or ignored altogether. In other words, pulse, meter and groove were not an essential element anymore. Another key ingredient was atonality, where musical pitch was no longer relegated to the conventional tonal system. Shrieks, barks, split tones were all part of this new sonic world.

Free jazz continues to emerge as a viable form of expression, and is actually less controversial.