1. Free Jazz improvisation doesn't use preset progressions of chords. In some cases it also dispenses with preset melody and steady timekeeping.
2. Be comparison with bebop, free jazz uses a wider variation in pitch and tone quality.
3. Some free jazz involves lengthy collective improvisations that are loud and frenzied.
4. Free jazz drummers often generate an ever-changing undercurrent of activity instead of playing standard time-keeping patterns.
5. "Modal Jazz" is the term applied to (long) improvisations accompanied only by (one or) two-chord, continuously repeating patterns (or stagnant harmonies) and guided by notes in a scale (called a "mode"), rather than by notes in (a cycle of several) accompaniment chords.
6. The biggest names in modal jazz were Miles Davis and John Coltrane.
7. Pianist Bill Evans was pivotal in moving the Miles Davis repertory (selection of songs) to a modal approach, and his piano style influence Herbie Hancock, Chick Corea, and Keith Jarret. He also perfected a rhythmic approach that did not make the beat as obvious as previous jazz piano styles did.