Thanks guys for your support. I don't believe the GR55 sends cc messages for this so it is an internal proprietary function.
The looper idea is OK but getting the timing to work over it would be very difficult as you mention.
A straight sustain (cc64) only replicates the fourth version of the hold function as described in the manual above (HOLD 4)
But follow me on this and I think I can replicate unless you guys have a better idea. (I am still learning MainStage)
What if you created two identical patches.
One the first one the triggering of the sustain pedal would also advance to the next patch and hold the sound from the prior (I think you can do that)
One the second patch, you can either mute all notes, to replicate one of the hold functions (HOLD 2)
Or , you can play them normally without sustaining (HOLD 3)
You can then program that patch to go back to the previous patch when you press the pedal.
This would require two patches for overtime you want to do this, but given there is no limitation there, I don't think that is an issue.
I also haven't figured out a way to replicate the HOLD 1 function described in the manual but I don't use that one so not a big deal.
Make sense? Any better ideas?
Thanks guys!!
MM