Basic MIDI, the receiving device is just receiving, unless you specifically program a sound to only respond to a certain range of Keys, it will respond to all 128, C-2 through G8, coming IN via MIDI.

On the HOME screen of any MONTAGE sound you can see the key “Range” that each Part is set to respond.

We can’t help you with the RD, but play on your MONTAGE, use the Octave up and down buttons to Transpose the MONTAGE... once you have convinced yourself it is working exactly as it should... then contact Roland for how to use it as a MIDI Controller. Let us know.

It would help if you can reproduce this issue on a standard factory preset and then advertise the exact name of the Montage preset used. I have an RD-2000 and can see if I can reproduce. But I need to know your Montage config first.

Also, what's the setup? How are the RD2k and Montage connected together? Through a MIDI cable or USB with a computer between?

BTW, I just tested this out and everything works fine.

RD-2000 MIDI OUT 1 (DIN) -> MIDI Cable -> Montage MIDI IN (DIN)

Montage: Set MIDI I/O mode to MIDI (not USB), recall Performance "CFX Concert"

RD-2000: Recall tone "Aco Grand7". Zone Fader #1 controls RD-2000 volume, Zone Fader #5 controls Montage volume. Or can press the INT/EXT button (which is red for RD-2000 meaning internal and green for Montage meaning external) to turn on/off each (RD-2000 or Montage).

There are lots of ways to route the audio. I currently have mine setup so both Montage and the RD-2000 have stereo outs going to a 4-channel audio interface which I use as a mixer for monitoring.

All 88 keys on the RD-2000 reach all 88 respective notes on my Montage 7. Been fun playing with combining the RD-2000 piano sounds with the CFX sound to see what sounds best and "A-B" the sounds by cutting off one vs. another yet play the same piano keys.

Now "CFX Concert" on Montage has the upper keys in PART 3. So this shouldn't be working unless I have my keyboard set to Single-Channel MIDI mode (under advanced settings). I checked - and see that I indeed do. Single channel MIDI mode with I/O channel set to Ch 1. This matches the RD-2000 zone #5 which shows Ch 1 for the transmit channel.

If I had Montage set to multi-channel MIDI mode - this will work, I just need to do some editing on the RD-2000. This only works to the limit you have free external zones free on the RD-2000. What I mean by this is say you have 3 internal sounds using zones 1-3. If you have the Montage in multi-channel mode and need to control a Performance that uses 6 PARTs - you will run out of zones. 3 internal zones only leaves 5 external zones - but this hypothetical Performance requires 6 zones. You would need to either set Montage to singe-channel mode or remove a PART (possibly by using a single-PART instrument, if you can, vs. a mult-PART version).

1) I set Montage to multi-channel mode
2) Now starting from the 2nd to last G# (on top) - sound cuts out because this is the range where PART 3 is required. I'm currently not transmitting on MIDI CH 2, 3, or 4 - so this is why the whole range isn't covered. Also, PART 4 is note-off (release) sounds. They are not happening. It's harder to hear this is missing.
3) RD-2000, I press the INT/EXT button for Zones 6, 7, and 8. Lighting up these 3 buttons as green (this is the default - green=external). They are already set to Zone 6 = MIDI Ch 2, Zone 7 = MIDI Ch 3, Zone 8 = MIDI Ch 4. That's all I need to get "CFX Concert" on Montage happy. G# on up, key release, everything.

If you change the level of Montage from the zone faders - be sure to move all of the external zones together. I had Montage set to a lower volume than default when I was combining with internal sounds. So I had to adjust zones 6-8 down to match 5. It's probably less of a hassle in a MIDI configuration to use single-channel mode if Montage is going to be a slave. If you stick with single-PART instruments on Montage - then leaving in multi-channel mode may not be bad if you want to be able for your master to adjust individual instrument volumes on Montage. Lots of flexibility.

Also a furthernote about "CFX Concert". PART 1 represents soft-to-medium velocities. PART 2 (not yet described above) represents high velocities. In multi-channel mode before I added channels 2-4 the piano sound would also not play if I played at high velocities. You may find either velocity ranges do not work, note ranges do not work, or entire PARTs are missing if you do not output all the MIDI channels needed from your master controller.