For that use case you would create a part that uses zones to communicate with your external device.

Bad Mister gives an example in this thread of how to do just that
https://yamahasynth.com/forum/control-midi-out-settings-per-performance#reply-120562

These will help get you started

https://yamahasynth.com/forum/send-program-changes-to-external-midi-keyboard-without-sacrificing-playable-part#reply-120280

https://yamahasynth.com/learn/montage/zone-master-faq-mastering-montage?_ga=2.222633371.1690327119.1646623325-1992780149.1646623325

http://sandsoftwaresound.net/yamaha-modx-zone-master/

https://www.youtube.com/watch?v=XM45p3Q6hIA

Here is a brief excerpt from another thread where Bad Mister shows step-by-step how to use zones:
https://www.yamahasynth.com/forum/how-to-create-a-performance-using-an-external-sound-module-and-the-modx-please-help-organ-sounds

But what you can do is build a Part slot (called a “Zone” ) which will be designed specifically to control that external synth.

You will be able to play it from the MODX keys, you will be able to mix the two with the Super Knob, you can smoothly morph between them, or even abruptly switch from one to the other. You will be able control the external synth’s Volume, Pan position, even apply MODX’s cutting edge effects to it.

This is possible by using the MODX’s “Zone Master” — Master Keyboard function, and by plugging the main audio outputs of that synth to the AD Input on back panel of the MODX. This will give you the maximum control over the combination.

Below is gathered from several of my recent previous posts… take your time… if you get stuck, post back.

Building a Part/Zone slot for your External device
. . .

[quotePost id=120863]greetings , can I get video links and tips showing the fine settings of playing montage performance with two keyboards by managing a specific part or parts (by spliting the second keyboard ) in the montage performance with a second keyboard[/quotePost]
Sounds to me that the original poster wants to use the second keyboard as a Controller (not as a Tone Generator) __ I mean why would you ask here for how to split your second keyboard without identifying it. I think it likely they are interested in using that second keyboard, (along with the MONTAGE keys) to play some sounds with the MONTAGE and other sounds with the unnamed “second keyboard”… I think, perhaps, they want all the sounds to come from the MONTAGE. It is not really clear…

(“Zone Master” is designed exclusively for using the MONTAGE as a Controller. It would only apply in situations where you’re using the MONTAGE as a master keyboard controller).

But I’ll wait to get confirmation before sending them of on a reading tour…
Dogukan, it would be helpful to know the following:
__ how many MIDI channels the “second keyboard” can transmit on simultaneously
Because if it is more than one channel at a time that completely changes the possibilities and therefore, changes the answer.
__ whether you want all sounds to come from the MONTAGE outputs or do you want to create a split where the lower split is the second keyboard sounding, while the upper split is MONTAGE.
__ specify an example. Dealing with Single Part and Multi Part MONTAGE Performances can require different approaches.

Let us know, please. The more specific the question, the more targeted the reply.

[quotePost id=120868][quotePost id=120863]greetings , can I get video links and tips showing the fine settings of playing montage performance with two keyboards by managing a specific part or parts (by spliting the second keyboard ) in the montage performance with a second keyboard[/quotePost]
Sounds to me that the original poster wants to use the second keyboard as a Controller (not as a Tone Generator) __ I mean why would you ask here for how to split your second keyboard without identifying it. I think it likely they are interested in using that second keyboard, (along with the MONTAGE keys) to play some sounds with the MONTAGE and other sounds with the unnamed “second keyboard”… I think, perhaps, they want all the sounds to come from the MONTAGE. It is not really clear…

(“Zone Master” is designed exclusively for using the MONTAGE as a Controller. It would only apply in situations where you’re using the MONTAGE as a master keyboard controller).

But I’ll wait to get confirmation before sending them of on a reading tour…
Dogukan, it would be helpful to know the following:
__ how many MIDI channels the “second keyboard” can transmit on simultaneously
Because if it is more than one channel at a time that completely changes the possibilities and therefore, changes the answer.
__ whether you want all sounds to come from the MONTAGE outputs or do you want to create a split where the lower split is the second keyboard sounding, while the upper split is MONTAGE.
__ specify an example. Dealing with Single Part and Multi Part MONTAGE Performances can require different approaches.

Let us know, please. The more specific the question, the more targeted the reply.
[/quotePost]

1) my second keyboard is hammond sk pro and has 16 midi channels. At the moment I can play both keyboards by connecting the hammond to the YAMAHA montage from the A D input and hearing both keyboards through the phone output of the montage. Would this be a good choice for live performance or is it much healthier to enter the mixer independently using two separate stereo channels?

2) Let me try to learn all the connection options of both keyboards with as complex an example as possible.
a). I want to hear both keyboards through the phone output of the yamaha montage
b) I want to be able to reach and play the tones of my hammond keyboard, as well as turn down the original hammond sound when necessary, using the super knob, I want to hear the sound of part 8 on my yamaha montage performance on the hammond.

I apologise for my late reply. Although I am an old motif user, I have not yet had the habit of using the forum, which I discovered in the first days I bought a yamaha montage FEBRUARY 2023 , I only saw the first responder of this question and did not read B. D's answer. I was able to solve certain connection options with midi connection, but now it's time for more complex connections 🙂 In fact, since I am not a professional musician but an active engineer, a general thanks to the yamaha family for the past 5 months, who gave detailed answers to even some simple questions I asked.

1) my second keyboard is hammond sk pro and has 16 midi channels. At the moment I can play both keyboards by connecting the hammond to the YAMAHA montage from the A D input and hearing both keyboards through the phone output of the montage. Would this be a good choice for live performance or is it much healthier to enter the mixer independently using two separate stereo channels?

Whether it is the right choice for you is something you must decide. The important thing is that this is certainly an option. But as you might imagine there are many options open to you.

Part of the design concept of the MONTAGE was to include external devices within the Motion Control Engine. Audio Input can be not only just fed to the outputs but can be used as a modifier within the synthesis engine.

We now know your external keyboard has a set of keys that you likely want to play directly (hands on)…the organ interface (drawbars, waterfall keys, etc) invite direct contact.

2) Let me try to learn all the connection options of both keyboards with as complex an example as possible.
a). I want to hear both keyboards through the phone output of the yamaha montage
b) I want to be able to reach and play the tones of my hammond keyboard, as well as turn down the original hammond sound when necessary, using the super knob, I want to hear the sound of part 8 on my yamaha montage performance on the hammond.

I believe this is entirely possible (I don’t know anything about SK pro) but unless there is something unusual… nothing can prevent this. You can setup Performances that have internal MONTAGE sounds and a Part slot dedicated to the SK Pro.

And because you’re additionally returning audio to the MONTAGE’s AD IN, you can use the Super Knob to morph between internal MONTAGE Parts and the SK Pro’s Part slot,

You should be able to establish a 5-pin MIDI connection OUT from the MONTAGE to the SK Pro. Setting up Part slot #8 to address the external synth will allow you access to a front panel Slider to Control external Volume. Even if you are not using MONTAGE’s keys to play the SK Pro, you can still address it from your MONTAGE controllers.

And because you are returning Audio from the SK Pro to the AD IN, you can control the Audio In with the Common Assign Knobs and Super Knob.

There are several options.