Bebop, one of the most intellectually demanding movements in American music, was named after a nonsense scat syllable that 1940s club audiences used because they had no other word for what they were hearing. This episode traces the revolution from the rigid, dance-driven big bands of Benny Goodman and Glenn Miller, through the looser Kansas City sound of Count Basie, and the boundary-pushing of Lester Young, Art Tatum and Coleman Hawkins's 1939 recording of Body and Soul.

The conversation moves to the after-hours laboratories of Minton's Playhouse and Monroe's Uptown House, where cutting contests, five-piece combos, ride-cymbal timekeeping, dropped bombs and walking bass lines rebuilt the rhythm section. It explains Charlie Parker's Cherokee epiphany about upper chord intervals, contrafacts, rootless piano voicings, the 1942 to 1944 recordi ...