I have not used a GR33 or a VG88, I do own a GR09 (which pre-dates the GR33).
The GR09 does have MIDI in and out and I have used it as a sound module, triggered by a keyboard, via Cakewalk. I had no problems at all - it triggered just as well as most of my other modules. I must assume the GR33 has MIDI in - but I don't really know anything about the VG88.
