I have two iPod Nano's that I take to the gym. One has classical and opera: Verdi, Puccini, Rossini, Mascagni, Bjoerling, Price, Rachmaninoff, Franck, etc. The other is rock: about half Fifties (mostly doo-wop but also Fats Domino, Buddy Holly, Big Joe Turner, Elvis); the other half Sixties with some later (Hendrix, Stones, Beatles, Elton, Who, Clash, Segar, Wonder, Beach Boys, Cream, Fleetwood Mac,etc.).