"If you keep your head and your ass in the same place, that'll happen on its own," says Jason Isbell on how he gets the most out of his live performances. On the heels of a new HBO documentary, he and Cory sit down for a deep discussion, talking creating genuine art that can also turn into hits, Muscle Shoals, and the intersection between "guitarist" and "songwriter"—as well as "for life" gear choices.