Is it possible to have the MOX receive only patch change messages from my red stage piano? (no note/velocity/system data)

Hate to answer a question with a question but… but do you have a way to filter “note/velocity/system data” from your red stage piano? The issue is one for the keyboard acting as the MASTER controller - so it is a transmit problem, not a receive issue. In general, anything you change on the receiving device will prevent YOU from playing it too. So you want to make the changes on your Transmitting device.

If you were using the MOX as your MASTER controller I could answer you:
Yes, you would go into MASTER mode…
Activate a ZONE to control your external device
Set the NOTE RANGE on that particular ZONE so that the LOW NOTE LIMIT = G8 and the HIGH NOTE LIMIT = C-2. This creates a “no-fly” zone for that entire ZONE output. Meaning you can send Program Changes without triggering any sounds.... etc., etc.

Since I don’t know your “red stage piano”, you have to ask the question of the little ‘red stage piano’ company:

Is it possible to have my red stage piano TRANSMIT only patch change messages to the MOX?

Hope that helps…