By Anna Fasolino “Good morning, Captain!” 21-year-old Abby Hartley’s clear voice sails through the loudspeakers over the RV park in Waldron, Arkansas. She’s singing the opening lines of “Mule Skinner Blues,” a bluegrass classic she has performed since she was 8 years old. Later she and 13-year-old Micah harmonize on their fiddles in a beautiful […]