Sonny Osborne bolted a padlock onto the resonator of his banjo to keep rivals and angry traditionalists from seeing the electronics inside. This episode explains how a prodigy born in Thousand Sticks, Kentucky, in 1937, who was playing the Grand Ole Opry with Bill Monroe at 14, grew into the most controversial innovator in bluegrass alongside his brother Bobby.

We follow the Osborne Brothers from RCA sessions with Jimmy Martin and Red Allen through the rock and roll era that made labels like MGM nervous, the 1960 Antioch College show that opened the college folk audience, and the 1967 recording of Rocky Top that sold 80,000 copies in its first month. Then the heresies: pedal steel, piano, drums, individual pickups instead of a single microphone, a patented six-string banjo, and stacked vocal harmonies built like a wall. We cover the 291,000 miles in 26 months, the 1971 CMA Vocal Group of the Year award, the first bluegrass performance at the White House in 1973, and the surprising irony that the great modernizer rejected the chromatic banjo style as a shortcut.

• Hired by Bill Monroe at 14 and what starting at the summit does to an artist
• Why purists saw a snare drum and a pedal steel as an attack on Monroe’s template
• The six-string banjo as an engineering fix for a dense, amplified mix
• Horn and piano phrasing translated to a percussive instrument
• Rotator cuff retirement in 2005, the Bluegrass Today column, and the Hall of Fame