> What about adding a switch so that the keyboard and the incoming midi data
> is not processed at the same time

I'll ask Christian if it's possible at all (may be the memory of the PIC
used in the circuit is not sufficient) and how many hours of work would be
required to add this feature to the A-100CGK firmware. In any case it cannot
be realized short-term as there are some other projects that have to be
finalized (e.g. USB version of LMK4, VC DSP effect module A-187-2,
polyphonic Midi-to-CV/Gate interface A-190-3, CV/Gate-to-Midi interface
A-192-2, USB version of CTM64 with LEDs for each button).

Best wishes
Dieter Doepfer