One of the most enchanting and haunting groups I ever discovered was this group of British women who take existing songs/poetry etc in old english, latin, gaelic etc (ie pieces from what would be called the medieval period) and give them modern twists, beautiful acapella renditions, or very period (with period instrumentals as accompaniment) recordings.
I have yet to see them live - though I would love to. They do the ren faire circuit, but never seem to make it up to the NY festival in Sterling forest that I attend.
I love these gals for their voices, their talent, and their body of work. And, yes . . I'll admit, I am a big ren fair geek and have been for ages.
More about them here:
The Medieval Baebes website - http://www.mediaevalbaebes.com/