If all robots were musicians, the best instrument for them to play would be the theremin. This is because it creates delightful scenarios in which the robot can play its own space-age soundtrack music.
Take Lev, for example. The theremin-shredding bot, built by Ranjit Bhatnagar at Moonmilk Laboratories, is featured in a couple of mesmerizing videos below. Both are "Crazy"--one by Patsy Cline, and one by Gnarls Barkley in which Lev is accompanied by a robot drummer called Thumpbot.
Lev's been playing the theremin for a while; according to the Moonmilk site, the robot played a performance at the Artbots 2003 show in New York. But the YouTube clips are new, so lay off. Jeez.