Haven't tried this with a "dumb" MIDI controller - since I do not own one. I have a Korg with micro keys - but it only has 5-pin DIN connectivity.

I did try Montage-to-Montage which doesn't work.

Hello Reinhard - I'm trying to figure out why you'd want to do that?

@Jason: Thanks for your reply!
@Rod: I'd like to attach a small external keyboard or pad controller to play Sounds from the Montage without adding too much complexity to my rig. Having a separate keyboard makes some things easier/more logical on stage 😀
The Midi-In aren't available to me, as the Montage is already connected to Ableton via USB. I already control the Montage via Ableton, so routing a keyboard through Ableton would be possible, but I'm trying to make it as "standalone" as possible. Even thinking about replacing Ableton with the MPC Live 😀

Although you could go the MIDI/DIN route with the external keyboard - Ableton receives this data through port 3 - then "echos" it back to Montage.

Using USB MIDI does not completely cut off the external MIDI in.

I use a midi-merger for additional midi-keyboards and a midi-foot-switch (Behringer FCB1010).
It is small device with four in, one out to the Montage. Works perfectly and has priority intelligence. I do not notice any delay.
With the external keyboards I address parts 9-16. It also has some pads with which i can trigger one-shot effects at one of the 9-16 parts of Montage.
The foot-switch I mainly do use for changing scenes, when I can't release my hands.
In Holland it costs around 50 euro.