“Voices of Gullah” members (from left), Joe Murray, Minnie “Gracie” Gadson, Rosa Murray and Charles “Jojo” Brown, sing Gullah spirituals on July 19 at the Brick Baptist Church in St. Helena Island.

A two-time Grammy Award-winning Charleston band has helped put Gullah music on the international map, but it's been a part of South Carolina's coastal culture for centuries now, tracing back to ...