LEMUR is a Brooklyn-based group of artists and technologists developing robotic musical instruments. Founded in 2000 by musician and engineer Eric Singer. Here are a couple of their instruments and I recommend checking out the videos on their site of them all in action.
!rBot is a mollusk-like structure made of leather, aluminum and steel. A mechanical system of cams and levers powered by two motors opens and closes !rBot's shell. As the shell opens, a platform holding a shaking percussive rattle protrudes from the robot's interior, receding again as the shell closes.
A robotically controlled percussive musical instrument that creates both atonal rhythms as well as tonal droning soundscapes. The instrument is based on the tones produced by three Tibetan singing bowls struck by six robotic arms, two per bowl.
GuitarBot, is an electrified slide guitar that is versatile, responsive, capable of fast and slow playing, easy to control, with high-quality sound, modular and portable. Its purpose is to extend, not simply duplicate, the capabilities of a human guitarist.