There're robots which can play music. WABOT can play the electone, Maywa Denki Singing robots(?) can play music. In 2003, a music player robots exhibition was held at Xebec hall Kobe. They had only robots' arms and played drums, that was live and so powerful. Suguru Gotoh, an artist living in Paris, made a suggestion those robots, and he's plannning to produce a 25-piece-orchestra. In 2004, I saw GuitarBot at NIME International Conference. Lemur research group produced it, and still working on various kinds of music robots. TOYOTA presented a trumpetter robot in order to Expo 2005 AICHI, Japan. I saw it on TV and was pretty good job. According to a book I read, the Univ. of Electro-Communications created a violinist robot, Violin Mubot. Drummer robots

Nowadays we can play music in pretty good sound with computers and DTM. Why do we make robots to take the trouble to play music? One reason is that is a research. It's useful to know a mechanism of playing music. Also, concerning about art performance, it gives so much presence. Can you imagine "live music" with PC and MIDI at a concert hall?

Let me say in passing that we have seen auto-play instruments for long time. I saw an auto-play violin and banjo at Musix Box Museum Rokko.