Other keyboards do not do this because other keyboards work differently. Even within other keyboards, the MIDI implementation is slightly different on how they elect to implement "zones", "splits", "layers", etc.

If you have Montage setup for multi-channel MIDI mode, then each PART will send a MIDI message assuming Part Zone settings have not switched MIDI transmit OFF.

So if you see 3 notes going through MIDI OUT - then your performance is at least 3 PARTs. If you do a [CATEGORY SEARCH] and select one of the green-colored performances -- those are single-part performances -- then chances are you'll only see one note at a time when you strike a key. The first one in the list is "CFX PopStudioGrand" - load that and notice only one (not multiple) MIDI notes on/off messages per keyboard key struck.

Compare this to "CFX + FM EP" - which you will see 5 "repeated" notes because, look at the main screen and see there are 5 PARTs.

All of this is completely under your control. I think it is best to take a step back and understand how Montage works as a big-picture so you can understand how to utilize Montage as a MIDI device both to bridge what you know from other keyboards - and to know how to use any new/differentiating features to get even more.

Montage has 8 PARTs that can simultaneously respond to your local keyboard keys - local meaning the white and black keys "piano" keys you paid for when you bought the Montage. These local keys can control PARTs 1-8 all at the same time. And PARTs 1-8 can be setup to respond to the same note (layer). PARTs 1-8 default to output to MIDI channels 1-8. So Part 1 = MIDI channel 1, Part 2 = MIDI channel 2, ... Part 8 = MIDI channel 8. You can change this MIDI channel assignment by using Zone Control (master = on, Part = on, then any PART's Zone MIDI transmit channel set to any value you want 1-16). That's a "nuance", not big-picture.

Since each PART 1-8 can simultaneously respond to a single key press - you will see MIDI output for each PART which you have assigned to a MIDI output. Either the default or the Zone channel (unless OFF). The only way to stop each PART (while in Multi-mode) from sending a MIDI message is to enable PART Zone Control and set the output MIDI channel to OFF.

It may seem counter-intuitive that you have to turn ON Zone control in order to turn OFF MIDI output - but Zone control (PART level) is the only place you can set an individual PART's MIDI output to OFF. There are other options available - I've hinted at multi-channel vs. single-channel MIDI I/O.

Setting your keyboard to "single-channel" mode - then the Montage will mostly "act" like other Keyboards. I'm not sure this is a good thing to just switch Montage to this mode simply because it may be more familiar. It's important to understand some of the basics of the tool in front of you and to use the right mode for the job. Meaning, the mode which gets the keyboard to do what you want. Familiar may not always be the best tool for a job at hand.

Note that all of the performances are acting as they should. The "Multi Saw MW DA" performance is green - a single-part performance. Only one PART only one MIDI Channel.

The 3-note performance is going to have 3 PARTs assuming it is a "stock" preset.

Some other threads:

https://www.yamahasynth.com/forum/montage-as-master-keyboard-explain-zone-relationship-to-montage-parts
https://yamahasynth.com/forum/every-note-from-montage-being-recorded-5-times

Hi Byron,

The solution is in this thread: https://www.yamahasynth.com/forum/using-montage-as-a-multi-timbral-sound-device

Basically turn off the keyboard control icon for all but one part if your DAW auto-channelizes, or if it does not then turn off the keyboard control for all parts except the one you are recording. This will allow you to be in Multi-I/O mode with all channels receiving and only one transmitting at a time.

Spoff

"The solution" is really a matter of what you're trying to accomplish. To me, it's best to understand how the system works so you know when you elect to use various options and configurations that there's a real understanding of what's going on with all the moving parts (Montage internals, montage external data flow, DAW interaction and options).

Because depending on the "one thing" you're trying to accomplish - there may/probably a handful of methods that work equally as well to accomplish the task. Selecting the workflow that best suits your particular expectations is a personal preference.

Most suggestions are a jumping-off points to help with understanding. There are a handful of "rules". ... and there are many choices.