I did this one Saturday using the Genos. There are several reasons I stopped using it. One reason is that I keep missing chords, not being used to 76 keys. You'll hear that in the guitar ride. Another reason is that I'm spoiled by the Korg vocal harmonizer. I'm too used to being able to engage it WHILE I'm singing a note. In time I would adjust to both of these things.
Anyway here's Blue Christmas:
Blue Christmas on Genos