Here's a link to the OnStage forum.
I have written several posts on this subject. The creator and moderator, Vic, has also lots of info on there. You need to know a little about midi messaging, but that's fairly easy.
http://www.playwareinnovations.com/forums/viewforum.php?f=2&sid=0e34aa8d6b2d11ae661f75a31e111b25

Another I have found is this: http://www.alienapparatus.com/products.html

Even more links: http://www.hitsquad.com/smm/win95/LIVE_PERFORMANCE/

Good luck!