I often listen to the Mediæval Bæbes while painting (and not just painting
Brets, but it is very appropriate music). They sing medievl music and poetry set to music, as well as original compositions in the medieval style.
I even called My Heavens Prophetess '
Kilmeny'
If you want something a little more contemporary... Off the top of my head:
Chosen Ones
Lift thine Eyes (From Medieval Total War II (EDIT- Bohemond beat me to it!))
Sail Away to Avalon