Instead of just playing midifiles why don"t YOU play Christmas styles? That would be a great sing a long!!! I put together a styles disk of 50 christmas styles tweaked for PSR2000 + OTS. It's available at http://psrtutorial.com/Files/F_Styles/S_Other/s_other.html
Look for Charley's Gems 6 disk. It's also in the files section of the Yahoo PSR2000 group.