I first heard this song when the 45 single was delivered to the college radio station I was working at.
from Shawn's website: "The Christmas Song was written in a hotel room in Rome, in 1969. I can't remember what I was in Rome for, but it was close to Christmas, and I started thinking about that, and all that entailed, and I wanted to tell the story somewhat differently, and make it fun. A few months later, when we were recording Second Contribution, I played the song for Jonathan Weston, and he didn't want to waste any of the studio time we had. I was determined to get it on tape. So when he and the engineer Robin Cable went out for a dinner break, I got on the phone, and gathered together 19 musicians, and I had everyone of them set up with microphones, and had the levels set, we'd rehearsed it several times, and we were sitting in the studio, and then Jonathan, and Robin walked into the control room. I just told Robin to roll the tape. It was done in the first take."
Actually, on the recording, which you can get for a nominal fee from itunes, there's a bit of a false start, that isn't heard on this video. Shawn gives an infectious, joyous laugh and says "I think that's tremendous" and then launches into the song.
I think I love that laughter as much as I love the song.