Yesterday I was reading a book about Dutch painting, and it had a small reproduction of a painting you can see on this page

http://www.phxart.org/collection/euro_collection.asp

It is called 'Interior with Girl Playing Guitar' by Pieter Janssens Elinga. It is dated 1655-1665.

I like the way she has kicked her shoes off and has left items lying on the floor. She'll pick them up later, but right now music is more important.   

The next time somebody tells me that guitar is too new-fangled for early music, I will be prepared.