One I may've missed but it's been so long (3 January this yr.) I can't be sure: Canuck jazz keyboardist Paul Bley.
In 1957 Bley stayed in Los Angeles where he led the house band at the Hillcrest Club. By 1958 the original band, with vibes player Dave Pike, evolved into a quintet with Bley hiring trumpet player Don Cherry, alto saxophonist Ornette Coleman, bassist Charlie Haden and drummer Billy Higginssez the Wikipedia. The YouTube states:
Just as the famous 1940-41 Jerry Newman recordings at Minton's and Clark Monroe's Uptown House captured the transition from swing to bebop, the music on this CD (compiled here on one set for the first time ever) marks one of the first steps from bebop into what would soon be called "free jazz". The whole quintet consisted of modern players working with the same concept: a freer way of playing jazz, which transcended the strict confines of melody, harmony and rhythm. They would create a whole new idiom by constructing music via the interplay of simultaneous collective improvisation.