Each element can be assigned a Midi function, which is triggered when activated.
TouchOSC is an inexpensive app that allows us to create touch control surfaces with various control elements, fader's, encoders, buttons.Note that I am using this as a CC control surface and am not using OSC back from my DAW (it does not support OSC). Setup was simple using TouchOSC Bridge to handle MIDI over LAN.
There are setup and use instructions on their website that are easy to follow. This can be changed by ctrl + clicking on the icon next to the Keyswitching padlock. Type: Controller - by default MIDI CC 32 is used for UACC Keyswitching.
Once complete, go to the Output Menu where the following should be selected. 2020 orion rxb 250 Taonga pounamu wellington