First, take a look here: http://faq.yamaha.com/us/en/article/musical-instruments/keyboards/synthesizers/montage/11002/9295
Above represents a more convental solution than below. And I haven't tested below to see if it works.

Wish my "recovery time" could be quicker from playing a gig or practice. So keep in mind, I'm flying blind without the keyboard to test this. I'm going to be leveraging your feedback and speculating vs. doing 1st-hand testing. Hopefully it will be somewhat helpful at least as something to try.

As far as the volume control - I'm not sure how master volume of a tone engine translates out to part volumes sent out to the matching MIDI channels for external controls. Maybe there's a setting and options here - but I would think what you want is to achieve, with your pedal, what would happen if you had part 1-8 or part 9-16 (where the range of your external parts are located) faders were used to set the volume.

To do this, I would think you can setup superknob to move the global assignable knobs, in turn these knobs at each external MIDI control PART control that PART's assignable knob (1-8, picking one) and that PART assignable knob controls part volume. Then an FC7 would be set to control superknob and this would be your volume control for the NE5.

This configuration should give some flexibility of independence from the main volume. Although superknob could also target volume control of the internal tone generator PARTs as well to tie the volumes together.

There's different ways to accomplish this. Since FC1 and FC2 (foot controllers) are "control box sources" - meaning they can be the source of control for the part volume, just like I've used assignable knobs in above - you can skip the superknob setting and use FC1 (for example) as a source for the volume control instead of an assignable knob. Superknob gives you a dial to grab for changing volume and two buttons to push for setting the volume to two default "discrete" values. Also automation with superknob is available if that is ever something down the road you want with volume.

Maybe there's an easier way - but that's what jumps out as a possible solution.

Now I'm not at home but if I underdtood correctly you suggest to use super knob to control volume of all parts included the one (for example part 8) assigned to external keyboard (in my case NE5). That's could be work around but to me seems very strange that pedal volume connected on montage act only on montage and the volume message are not send to external keyboard connected to montage. With other setup anytime I've used pedal control connected to master keyboard (in my case montage) the volume message (or expression message) was sent also to connected controlled keyboard(in my case NE5). It is very strange that montage "filter" this kind of signal.
Maybe bad Mister can indicate me the best way to set montage to control external keyboard in couple with montage. I hope.

I've solved a volume and expression problem. It was not a montage problem but a NE5 setting problem.
So I can Tell now that montage transmit right control volume by perdal.
It remain the problem to manage different situation (like scene do) controlling external device. In my case, for example, I use NE5 to do organ and I wanna switch between external and internal sound in the same song or layer both external and internal sound source in function of the piace of the song that I am. I can do that with the scene if I use only a montage or I can do that with set list of NE5 if I only play NE5, but I can't do it by controlling NE5 from montage. That's because scene can't in anyway controol any volume parameter (or mute parameter) of external part by mean of internal part assigned to external device (for example part 8). More if I put green keyboard controol of external device (on a prt 8 for example) this part sond in anycase also if I putted it muted or with zero volume so it is impossible to manage it. If I put green control keyboard of part 8 off, I can use only part 8 alone without the other montage part in layer because it work like a parts 9-16 in this case (with keyboard controol off). So it is very frustating to can't use the part assigned to external device like the other montage parts.
I think that it should be a good thinks if next firmware upfating of montage will include a green keyboard controol in the scene function so that a lot of problem will be solved and a lot of possibilities will be addet to montage.
Personally I think that this sould be the best things that Yamaha should do on montage.
Thanks Jason for help.

I know you've resolved the issue by adjusting the downstream device (this is part of why I was disclaiming my suggestions were based off your feedback - initially pointing towards Montage). Just wanted to clear up something: my first advice was to go to the link provided and take a look at the Yamaha Montaget FAQ which walks through setup of volume control for parts using a foot controller. The second alternative suggestion was using the foot controller to move superknob which was assigned to part volumes - along with a note and "third" option that you could skip the superknob assignment and assign the foot controller directly to part volumes.

Scenes are for internal control - see https://yamahasynth.com/forum/scenes-1

It scenes ... I mean seems like a reasonable suggestion to expand scenes to be better suited for external control.

I'll have to setup my board to run through if there are any tricks. Take a look at the above link "scenes-1" to see if that helps. Also, it may be worthwhile to take a look at the FAQ link previously provided.

Thanks Jason, other workaround that could be used.....but I hope that yamaha will introduce some modification to better controol external device. 😉

I'm glad you found that nothing extraordinary need be done to control the volume of your external device. I am preparing an article on an approach to using the Zone Master feature...which will help you understand why innovations like Scenes, the Super Knob, Motion Control, etc., etc. do not become instantly available to your external devices. I think once you understand how Montage accomplishes what it does so brilliantly for itself (meaning internal Parts) you'll better understand why this isn't instantly available for a potentially unknown external device, via MIDI.

What is available to the external Zone is going to be limited to fairly standard MIDI Channel Messages (cc) and that the act of recalling the Performance Sends that data to the external MIDI device. (Heck, it would be a lot easier if the MIDI spec included a universal "Mute" command; it does not). Until then, there exist other methods to silence, on demand, communication to your external devices via standard cc messages; eventually, the article will even discuss some of those.

Your external device is external. So naturally a MUTE (recallable via Scene), which disconnects the internal Part from the Montage audio Output, will not work on your external device. The Montage has no way of disconnecting your Nord from its own audio output. When you understand what the Scene MUTEs do, it's fairly obvious that they will have no affect on your external device. (It's a "mixer" function, your external device is not connected in the same way to the Montage's internal digital mixer).

From my initial notes in preparing that article....

What does and does not work for external devices:
Scenes can dynamically recall volume settings, send amounts, Arp and Motion Sequence selection, Mute status, etc., etc., for the internal Montage Parts.
The Super Knob can dynamically control internal parameters and via a complex assignment system it can additionally control the Assignable Knob functions of the sixteen internal Parts (max. 8 simultaneously). But again, its innovation is targeting the internal tone engine.

For the external device you cannot use Scenes. You can, however, recall settings for your external device via the ZONE SETTINGS function available to each slot designated to control an external device: one volume setting which is initially sent when you recall the Performance, you can control the volume (Expression) of the external Part with FC, or by assigning a knob directly to send cc7 or 11; Additionally, a real time Fader can be accessed to control your external devices volume. The Faders send cc7 when that function is selected. Additionally, you can recall pan position for your external device (if it is indeed stereo and capable of panning). You can preset the Octave and semitone Transposition (which affects the Montage keyboard transmit data); you can Send a Bank Select and Program Change; and finally, you can define the Note region that will be transmitted from the Montage keyboard Out on that zone. ....................

We did add a sort of Zone Mute function in the last updates for the Motif XF (what it did was allow the Zone Transmit to be toggle On/Off via an associate button [1]-[8] for the possible internal Zones, [9]-[16] for the 8 possible external Zones). We'll see whether or not engineering can do a similar thing with Montage.

It obviously is a brilliant thing to be able to address things via Scene memory "snapshots" but if you understand this function as having developed up from the "digital mixer" that is built into the Montage it becomes clearer - Your external device is not really accessing that internal mixer in the same way as the internal Parts. Therefore, something easily accomplished internally via system signals becomes very different Out via MIDI. Yamaha is involved in the future of MIDI and its spec, so hopefully we'll see some of these innovations addressable for external devices (as standard). We can only hope...

The way to have a big improvement of montage under any point of view (also midi controol) is to add keyboard controol under scene. It immediately solve also this problem.

please inform Nord 😉 they need to adopt Yamaha System Exclusive! 🙂

Yes but if I change my nord with other brand than I've to inform also new brand.:D ...too brand.... is better if green keyboard controol is implemented in the scene so any brand work fine. I think this happen also with external yamaha device or not?

There is also MIDI routing type software or hardware you could throw at this to translate SysEx to something more native to the connected device if adoption of Montage SysEx would otherwise fix the issue.

The software (or hardware - two different implementations of basically the same idea) intercepts messages including SysEx and allows you to "script" a different outgoing MIDI message which uses parts of the original message. The flexibility is fairly "wide open" including doing math, etc - so these devices/software-solutions should fit the bill.

The hardware solution is more costly although likely less prone to failure - faster "boot time" - etc. Since it is a "one trick pony" (the hardware) - it may also do a better job overall of serving the function. However, software (in general) is easier to update / add features. Depending if you use this on the road or in the studio may factor into which solution you use.

None of this may meet your expectations. I'm presenting that there is a path - which is better than "you can't get there from here".

Also, I'm not sure how MIDI reacts (vs the internal tone generator) - but for the internal tone generator - switching/selecting a part which is set at keyboard control=off temporarily assigns keyboard control=on (at least for the tone generator) when the part is selected. Not sure if this can be leveraged in your environment.