Went to a couple of concerts on Saturday, as part of a early improvisation weekend. The first concert I attend was the Orlando Consort, who did an excellent job of providing a history of polyphony from the early 10th century to the 14th, via the music and talking about it. Here's a video of them from youtube (1st hit on query 'Orlando Consort')
The second concert was delivered by Stevie Wishart, who gave a performance on medieval music using the Hurdy Gurdy and medieval violin. She also talked about the music and instruments, and was very engaging - she clearly loves her subject. Couldn't find any examples on youtube of here using those instruments, but this is interesting:
Here's a pic of Stevie playing a Hurdy Gurdy.