If you can get the hardware talking to a simple patch (try the [hi] object maybe) then you can use [sel] or [route] to work with the indices for each button. From there it’s totally simple, look to the tutorials and help files for sfplay~ etc.

You’ll probably need a hardware converter for the guitar to get into the PC USB port. But if [hi] doesn’t recognize it, you’ll need to look to [serial] instead.