Originally Posted by Wikipedia

Modal jazz is jazz that uses musical modes rather than chord progressions as a harmonic framework. Originating in the late 1950s and 1960s, modal jazz is characterized by Miles Davis's "Milestones" (1958) Kind of Blue (1959) and John Coltrane's classic quartet from 1960–64.[2] Other important performers include Bill Evans, Herbie Hancock, Wayne Shorter, and McCoy Tyner.[2] Though the term comes from the use of the pitches of particular modes (or scales) in the creation of solos, modal jazz compositions or accompaniments may only or additionally make use of the following techniques[2]:

1. slow-moving harmonic rhythm, where single chords may last four to sixteen or more measures
2. pedal points and[3] drones
3. absent or suppressed standard functional chord progressions
4. quartal harmonies or melodies