Ben Reardon saw a robot playing a classical guitar in 1988 at a World Expo in Brisbane, Australia. It stuck in his mind and he has now done his own version using a Raspberry Pi, an Arduino and some servos to pluck the strings. It’s obviously much more complicated than that, and he explains the challenges in his blog which has photos of some of the build process and lots more of the finished product. There are several videos (one of which you can see below) of it in action. The intriguing part of the project is that he has programmed it to take in the logs from his firewall and convert it into music. Read more here.