What if they took a game like this, but it was controlled with a guitar? I'm not sure how it could all work - but the neck of the guitar would be the distance you have left to right on the screen, the places an object appears would be where you'd have to place your hand or fingers on the frets (and this is where it gets complicated) the notes could correspond to the color or shape of one of the objects(?)... using a pick on the strings would fire. If you've played the wrong note then the shot wouldn't affect the object.
Hmm. I don't know.
It might not work out to well. Since different objects could be fired at at will -if the key was to (say) play a song or something, and with there being too many possible combinations of how to go about finishing a wave/stage....