Love the Guaraldi trio album! It ain't Christmas without it...I also have "On Yoolis Night" by Anonymous Four, and it has some wonderfully haunting medieval stuff on it...also a tape I got in the UK years ago called "The Service of Venus and Mars" by Gothic Voices has some great medieeval Yule songs...
But I gotta admit, there is still a soft spot in my heart for a battered old 8-track (!!!) my parents had--A Dean Martin Christmas.
(ooh, I am gonna get it for that one!)
If making a holiday compilation tape I would include some of these more obscure items:
A Christmas Song, Jack Frost and the Hooded Crow, and Ring Out, Solstice Bells, and God rest Ye Merry Gentlemen, all by Jethro Tull
Come, O Come Emmanuel
O Magnum Mysterium by Palestrina
O Virgo (recorded by Libana)
Oaken Logs (lyrics by Circle in the Greenwood)
Yule Carol?? (by Darragh Nagle)
Gaudete by Steeleye Span
Red and Green by Maddy Prior
peg