Dec 26th '17, 05:34
Not Christmas music per se, but I have swapped out several ogg files on occasion.
Also I changed the opening music for Tempus Irae to the Dies Irae from Verdi's Requiem.
As for Christmas music, some of the chants as a background might make some o the levels pretty spooky.
I just play 'em; I don't know how they work.