I had always credited Jim Hall and Bill Evans for creating the groundbreaking guitar / piano duo in their recording "Undercurrent" in 1962. But maybe they were inspired by a Barry Galbraith and John Lewis recording 4 years earlier. I just found this recording of Barry Galbraith and John Lewis from the 1958 album "The John Lewis Piano" where Barry and John play 3 guitar / piano duets. John Lewis was the founder and leader of the Modern Jazz Quartet which pioneered Lewis's group compositions with improvisation on an equal billing. Interestingly, on the last session Barry couldn't make it and Jim Hall filled in for the final selection of the album. Maybe this put the idea in the back of Jim's head to do Undercurrent four years later? All were connected in the NY jazz scene, if fact, Hall and Evans played on a soundtrack recording written by John Lewis in 1959, and covered his tune "Skating in Central Park" on Undercurrent. The 3 songs are The Bad and the Beautiful, It Never Entered My Mind, and Warmelandn(also known as Dear Old Stockholm) - attached below. Enjoy!