It is MIDI powered but does it have a MIDI out on it? I may have missed you saying it did or didn't. I have an M-Audio Keystation3 and it can run on either USB or external power adapter. It will also output on both USB or MIDI, but not at t eh same time. It's a simple switch accomplished with 2 of the keys. I would also suggest a MIDI thru box if you don't already have one. A 1 in 4 out will allow you to connect 4 sound sources on different channels and just change channel on the controller. Probably much like what you do now.