If I may make an educated guess, it sounds as if you're trying to duplicate in software the functionality of your Roland EF-303 unit. Apologies if that supposition is wrong, of course, but as another similarly-impressed (why wasn't this unit more popular?) EF-303 user, I've been trying to do the same. So let me share with you what I've found so far.
You may of course, and you are not far wrong, except that the EF303 was actually the item I use to duplicate my modular system, and now Im trying to duplicate the same... except that it doesnt have to be as all in one as the EF303... just the functionality i descrobed would do---
Thanks for the suggestions, gonna get them.. (are they free and for mac? at least a try BEFORE buy ??)