I have an idea for a future request: it will be very useful to have a pipe for converting polyphonic inputs into monophonic output, with a necessary option to select note priority (last, first, highest, lowest note).
In case of use you may control two different synth modules - one polyphonic, the other monophonic - at the same time with one MIDI keyboard. The polyphonic synth will be played as usual, the monophonic synth will play e.g. the highest pressed note on the MIDI keyboard (highest note priority) for melody.
Other case: you may control a polyphonic synth and a MIDI step sequencer with one MIDI keyboard. The polyphonic synth will be played as usual, the step sequencer can be transposed with the lowest pressed note on the MIDI keyboard (lowest note priority) at the same time.