Seth Goldstein dropped me a line to let us know about a machine he created which plays tunes on a real a violin. This mechanical wonder was recently featured in the New York Times. Here is a link to the article on Seth Goldstein's RO-BOW. In the video, Goldstein explains the basic components of the machine and how they work together make the machine perform musical magic.
Machines that play the violin are not new -- some may be seen at The Morris Museum in New Jersey. Check out the wonderful book on the collection called Musical Machines and Living Dolls. Still, Goldstein's robot is of a differnet, more modern variety, capable of replicating any tune that can play on a keyboard. It works on some very unique and ingenious principles. Truly amazing.
You can find out more about Seth Goldstein on his web site, which has information and video showing his other pieces Why Knot? and Cram Guy.