you obviously haven't thought this out very well. MIDI is a way of triggering instruments. it doesn't actually involve sound, waves, or patches... its a triggering protocol. the sound comes from the instruments. here i'm turning AVS into a 'visual instrument' that makes pictures instead of sounds. So you can get note 41 of channel 0 (say) to reverse the direction of a movie instead of (or as well as) making a sound with your sampler.
if i wanted to trigger avs with the sound made by some MIDI instruments I wouldn't need any special software would I? just some cables
T