Yes, it isn't an `instrument', it's a human-computer-interface for musical purposes, as you say. One of the great advantages of computer music is the complete

Yes, it isn't an `instrument', it's a human-computer-interface for musical purposes, as you say. One of the great advantages of computer music is the complete decoupling of sound generation from any particular human means of controlling it. Unfortunately, because they can be manufactured so cheaply, keyboards (in the piano or organ sense) dominate as a real-time control device. (A lot of them don't even have channel aftertouch, never mind polyphonic aftertouch!) Not that there has been a shortage of activity in this area: there's a conference http://en.wikipedia.org/wiki/New_Interfaces_for_Musical_Expression http://en.wikipedia.org/wiki/New_Interfaces_for_Musical_Expr... and many niche companies making niche products, but nothing has ever really taken off.