Jazz transformed through distinct eras:

• Dixieland/New Orleans (1900s-1920s) — collective improvisation, everyone soloing at once over a steady beat
• Swing/Big Band (1930s-1940s) — arranged music for large ensembles; Duke Ellington, Count Basie, and Benny Goodman made jazz America's pop music
• Bebop (1940s) — Charlie Parker and Dizzy Gillespie played at breakneck speed with complex harmonies, making jazz an art form for listening, not dancing
• Cool Jazz (1950s) — Miles Davis answered bebop's intensity with understated, spacious playing
• Free Jazz (1960s) — Ornette Coleman and John Coltrane abandoned traditional harmony entirely, pursuing pure emotional expression