Cars had bumpers, televisions had only four channels, and my sweat smelled more sweet than sour when I spent many a Saturday night at the Concord, Ala., Community Center. It was a hometown version of the Grand Ol’ Opry, only with metal folding chairs.

Standing-room-only crowds filled the squat cinderblock building to hear local bluegrass musicians pick and grin behind two sheets of plywood that were laid on the floor…