The viral cup song from Pitch Perfect traces back to When I’m Gone, recorded nearly a century earlier by three relatives from rural Virginia. This episode follows A.P. Carter, his wife Sara and his sister-in-law Maybelle from Maces Spring to Bristol, Tennessee on August 1, 1927, where Ralph Peer recorded them in an empty hat company warehouse for $50 a song plus a half-cent royalty. By the end of 1930 they had sold 300,000 records on the strength of songs like Single Girl, Married Girl.

The conversation breaks down the division of labor: Sara’s autoharp and unadorned lead vocals, A.P.’s song-gathering trips with Black guitarist Lesley Riddle and the friction between oral tradition and copyright law, and Maybelle’s Carter Scratch, which turned the guitar from background strummer into lead instrument. It then follows the family to 500,000-watt border blaster XERA in Mexico, the 1939 divorce hidden behind a wholesome radio image, Maybelle’s standoff to keep Chet Atkins on the Grand Ole Opry stage in 1950, and honors from the Country Music Hall of Fame, a postage stamp and a Grammy Lifetime Achievement Award.

• How shape-note singing democratized four-part harmony in the rural South
• Why Victor’s hardware-software problem sent producers on field expeditions
• Thumb-picked bass melody and brushed treble rhythm: the mechanics of the Carter Scratch
• Border radio signals rumored to vibrate in dental work and hum on barbed wire fences
• Mother Maybelle and the Carter Sisters, Chet Atkins, and the bridge to the electrified Nashville sound