Cool Jazz: emerged in the late 1940s and early 1950s as a reaction to the complexity and intensity of Bebop, featuring a more laid-back and relaxed sound, with simple melodies and improvisations, and often incorporating elements of classical and folk music.
Hard Bop: developed in the mid-1950s and emphasized complex chord changes and improvisations, with a strong focus on rhythm section interplay and often incorporating elements of Blues, R&B, and Gospel.
Free Jazz: emerged in the late 1950s and early 1960s and marked a departure from traditional harmonic structures and rhythms, allowing musicians to explore more freely their improvisational capabilities and blurring the boundaries between jazz and experimental music.