I'm a huge fan of the Mediaeval Baebes. This music is absolutely exquisite, and their voices are absolutely phenomenal. Alot of the lyrics are pulled from medieval text and then put to period music. If you close your eyes you can almost imagine yourself sitting on a hillside watching a joust or snuggled up with your own personal knight. ;-)
I listen to a lot of their music when working on my historical stories and any time I need some mystical inspiration.
If you look closely you can see they are actually singing while wearing vampire teeth!