This Module is currently available.
Specs are approved by the manufacturerMIDI Four to One Combiner
Entineering MIDI Merge combines data from four MIDI inputs into one MIDI output. By applying rolling status, the MIDI data is compressed, even if the connected keyboards and controllers can't do this. If there is still more data coming in through the four inputs than can be sent through the single output, the "Overload" indicator lights up.
Entineering MIDI Merge 4-to-1 MIDI