In the latter half of 1997, John Prine spent a string of Nashville afternoons with his friend and record producer Jim Rooney in a suite at Spence Manor, the funky tower hotel on Music Row with the guitar-shaped swimming pool. They were doing what passes for work in Music City, listening to and comparing thoughts about vintage country music duets: George Jones and Melba Montgomery, Porter Wagoner and Dolly Parton, Loretta Lynn and Ernest Tubb. And older records still, with Kitty Wells and Red Foley, or Wilma Lee and Stoney Cooper.