MG + controller in MainStage?

MG is working great as plugin for MainStage. But. When I plug in a keyboard controller, it kills MG. (I’ve looked at Apple instructions for using two controllers, but they only deal with hardware controllers.) Also…
For standalone MG, when I change patches with a keyboard controller, sometimes it’s a sloooow change. Going from one synth to another in halion sonic, new patch loads fast. Going from a built-in patch, like drawbar organ, to a halion instrument, or to a kontakt instrument, that’s real slow. Like 3 to 5 seconds.
I’m not a midi wizard by any stretch. Using MG mostly with an electric viola, and it works really well. Highly addictive.

Mainstage has keyboard objects: these can be seen graphically.
But if an unbound midi source is coming in, it will automatically be routed via am automatic keyboard object.
the problem is that you can not bind MG plugin into a steady keyboardobject, because that would require the midi stream to have a steady name. MG’s AU gets a random trailing number, like “MIDI Guitar #3”, and the virtual midi port also gets this name. A normal keyboard object needs the exact name however…
So you have to use the automatic keyboard object for the MG midi.
You should try create a keyboard object for your external keyboard: this might avoid the keyboard’s midi from shying away the MG’s midi out of the automatic keyboard object
I know, I know: this is all terribly complicated. Regrettably midi routing is really not that convenient in Mainstage.

Standalone MG switches patches by loading and initialising plugins at the time the Program Change comes in. There is no caching (this might be something for the future). So the time it costs is purely related to the size and complexity of the plugins used, adn the speed of your harddrive.
Mainstage, Cantabile or Gigperformer have preloading of patches.