Bernie,

Best solution is to use a MIDI merge box (2 MIDI IN {connected from both MIDI out of your controlers} -> 1 Midi Out {connected to the Midi in2 of SD40} ):- https://www.fullcompass.com/prod/125514-...lYaAkqvEALw_wcB

The unit shown above is what we use at the lab and we are about to release a video showing how we control 2 modules with this units (focus is on modules ofcourse but you get the drift).
Thanks,