Hildegard has a nice singing voice and adapts the lyrics to fit the medieval context, which creates some interesting pieces.
Here's "Somebody I used to know":
Agal, doesn't do vocals often, and instead tries to reproduce modern music utilizing medieval instruments.
To be honest some songs work better than others since tempo is not affected, so part of it might not sounds like a typical old song even with the old instruments.
This is " Crazy Train"