Benson, spun-off from the controversial late 70's sitcom, Soap, proved to be a far more popular series than its parent. One example is a Christmas episode, first broadcast in 1982 (season 4). DiDi Conn (later of Shining Time Station) is on the piano for the medley at the end of the show. Just wait 'til you get to the ending, and Benson himself (Robert Guillaume) sings "O Holy Night".
Edit, 12/24/17: Most of the episode was taken down due to copyright concerns. In its place, we have only the caroling portion of the show, including "O Holy Night" and Kraus (Inga Swenson) singing the Austrian interpretation of "Silent Night":
Enough said! Rating: A.