SHAWN COLVIN All Fall Down [Nonesuch] Procuring master guitarist and Nashville alt-country staple Buddy Miller as producer ensures authenticity in the Americana world—just ask Robert Plant, who tapped him for 2010’s Band of Joy—but Shawn Colvin needs no such thing for her first new album in six years. Her history with Miller is very different. She sang in his band early on and later toured with him, Emmylou Harris and Patty Griffin as Three...