The Yamaha Keyboards like PSR750 thru Tyros have them built in already. The problem lies with GM being able to "read" the XG data.

However, the latest keyboards can also save in wave format right from the keyboard itself.

You may want to contact "Seeker" on here (Frank). He has a PSR and is also connected to the best PSR Forum on the net. Maybe they can record the slides and thumps you need? It is very simple to do on one of those keyboards and they sound as realistic as a real guitar.

Trax