In lower Manhattan last Friday evening, Jason Isbell, the songwriter and guitarist, told a story of a perfect night in New York. Isbell, who grew up in Alabama and lives near Nashville, was out with his friend Will Welch-an Atlantan who is now the global editorial director of GQ-and Welch led him to a bar on Sullivan Street where, that night, the music played was from the state of Georgia and most of the patrons were Southerners who'd come north and settled in the city.