Swamp pop, south Louisiana’s blend of Cajun rock ’n’ roll, New Orleans R&B, country and zydeco, lives a life of irony in its Southwest Louisiana birthplace. As gray hair grows on the music’s original musicians and fans, swamp pop is rarely featured at the region’s numerous festivals, clubs and casinos.

Many swamp pop classics were recorded in the tiny town of Ville Platte, home of Floyd Soileau’s Jin record label. The Evangeline Parish town, designated Swamp Pop Capitol of the World by...