Here's where I'm at now.
Using a simple program to inject sequences of bytes through Jack to GO I can now set up the stops to respond to controller messages on my desktop box. Using what is the same version of GO on the organ cpu with the same sequence of bytes coming from the Arduino GO fails to respond when 'listen to complex event' is pending. I've rebuilt GO on the organ box to ensure that it's the same version, and monitored the bytes going through jack, and it all looks identical, but no joy.
The events are logged in the GO message window, so they are reaching GO, but for some reason they don't get through to the right place?
If I run GO under gdb I see the bytes received, but I don't understand enough of the internals to track it down. It gets put onto a message queue and I assume some other thread is going to pull it off, but I don't know which file or function to look in to see what happens. Any pointers welcomed...
Bill