Bluegrass sounds like it has echoed through Appalachian hollers for centuries, but it is a 1940s invention shaped by jazz structure and named after one man's band. This episode unpacks the raw materials, Scottish, English and Irish fiddle traditions meeting the West African lineage of the banjo and the blues, and shows how Bill Monroe synthesized them into a strict new standard with his Blue Grass Boys, formed in 1939.

The conversation breaks down the genre's architecture: Earl Scruggs' three-finger roll that solved the speed ceiling of clawhammer playing, the jazz-derived breakdown where each player takes a break, the root-and-fifth upright bass that mimics a kick drum, the forward-leaning attack that makes the music feel like a runaway train, and the stacked vocal harmonies behind Monroe's high lonesome sound. It then follows the schism b ...