just a little post to inform you that mainstage, the app used for playing music live with a midi keyboard has a quite good accessibility builtin.
The app allows you to define a set of patches for your concert, but the great thing is that you change patches using your midi keyboard without moving your hands from the keyboard to the mac.
You can swith patches either going up or down from patch to patch, or also typing the exact number of the patch with your midi keyboard.
It is also possible to change the effect of each sound, browse the library of instruments and switch between various view mode.
For now, I have some difficulties on creating a new patch with the keyboard splitted into two parts, with 2 channel strips.
So, if someone will make a research for "mainstage", I can confirm that this app is quite accessible. Not the best, but surely usable.