Tropical Hunch

I have a CTK-7000 that I was able to seamlessly interface via MIDI with Garage Band running on my ancient iPad 1. Use it mostly for recording direct, but recently came up with a very easy way to make it practical to use (along with a tubes and timber Hammond) in a live performance setting. Would like to be able to trigger the Leslie chorale/tremolo in GB's B3 app from the keyboard, but no luck so far. This can be done with my mini-Korg 25 key controller with the press of a button, but can't seem to make it happen with the larger 7000. Any suggestions? And yes, am running through Channel 1.