I published a instrument control plug in for Ableton audio editing / performance software using the built-in Max for Live visual coding tool. The video below shows how I was able to connect computer vision software to play instruments and change effects parameters.
The logic I created for this detects the largest object the camera can find and then uses those X/Y coordinates to send out a 0-127 Midi CC to the instrument/effect parameter of your choosing. In my case for this demo I had a custom looping instrument that I wanted to effect by waving my hand in front of the camera. As I move my hand it changes the speed and loop begin/end points to get a kind of audio glitch effect.
You can download the plugin for free at my Github account
M4L_CV from Michael Romeo on Vimeo.