Hear What Happened to the Pop Duo? Hall and Oates. Marvin Gaye and Tammi Terrell. Sonny & Cher. Simon & Garfunkel. Pop duos used to be popular and successful. What’s changed? Hear Guitar Gems of the 1950s If you listen closely to 1950s music, you can hear some wonderful work on the guitar. Here are a few gems to get you started.