The general "why?" is easy: without proper configuration you are likely to to have an number of things happen. But once you create a setup that works for you, the software can memorize that configuration and use it each time you launch the DAW.

Rather than spend energy deciphering what happens without any configuration, let's skip that and go right to how to configure your system so that it is ready to work when you launch it.

You need to make certain preparations for working with Montage and a computer DAW of your choice. Both the Montage and your computer software can and must be configured. The Montage has four basic templates. Three of them are customizable.

The first is "Standalone" - you use this when working with Montage without a computer. (If you use this in Standalone while connected to the computer you make experience strange behavior).

The other three are customizable. From the factory they are:
MIDI Rec on DAW
Arp Rec on DAW
Audio Rec on DAW

And represent the most commonly used setups. These templates change the signal flow within the setup. It adjust the clock Sync setting, can change the Direct Monitor situation, etc.

On your DAW side you need to create the appropriate type of reception for what you want to record.

For example, if your goal is to record MIDI data, you need to create or select a setup template that sets up a MIDI Track set to receive the type of data you are sending. Remember unlike typical synths that transmit always on just one MIDI Channel, Montage can be transmitting information on multiple MIDI channels simultaneously. You need to setup your DAW to deal with this.

Some DAWs, when you create a MIDI Track will record anybody Channel coming in. But then rechannelize the data on the way back out. This is fine if you transmitting In on just a single channel. But if you transmitted Out from Montage on four MIDI channels and you return the dust to Montage merged to one MIDI channel... that's not going to work.

Create a receiving template that can deal with the Multiple MIDI Channel situation that is Montage.

We´ve been thru all of this. I had everything set up, I recorded a song and now that I want to work on it again I am back to square one. Nothing works. I´m really depressed as I cannot make music like this. And I have very little hope at this point that I will ever get it to work. Because the settings are not changing. Cubase remembered them and still, things aren´t working.

The best way to learn this is one step at a time. You can't learn it by jumping in the middle or deeper ends of the pool. I recommend you sit down and construct a plan as to how to tackle learning the tool, before beginning to sculpt a masterpiece.

I would recommend starting to learn the Montage-Cubase situation by starting with recording Audio from Montage to Cubase.
To begin seeing how they work together, and how the signal flows between them, audio recording is best way to get your feet wet.

You'll need to understand audio routing in order to setup and do MIDI recording, so it makes sense to start by mastering audio transfer first.

Then once comfortable with audio, move to learning how to reconfigure your system for MIDI. To prevent listening to the audio twice you will need to make some changes. You will thoroughly understand the direct audio routing from audio recording... so now the addition of MIDI will be less challenging.

audio works fine. and midi also worked. I have all my tracks recorded and now I want to work on the drums (in midi) and once again, even thow everything is setup as it was when it worked, I cannot sync the montage with Cubase. I actually had to shut off my computer to make the montage stop drumming on it´s own, just shutting off Cubase didn´t make it stop. It´s crazy.

No, not really. The computer is typically setup to SEND clock commands (tempo) to the synth. The tempo driven functions of the Montage will follow the tempo reference from Cubase. The Montage has its own clock that runs the Arpeggiators, the Motion Sequences, the Tempo driven LFOs and Effects.

The Arps and Motion Sequences do not necessarily follow the Start and Stop commands of the DAW. This is understandable. Arp and Motion Sequences are started by touching the keys, not by starting a sequencer. The Arps and Motion Sequences are only started and stopped by your interaction with the keys, (and the Arp ON/OFF switch), although they reference the tempo of the DAW.

So they will not necessarily stop when you stop Cubase, particularly, if you are using the MIDI data to trigger the Arpeggios in real time. To stop the Arpeggios in Montage turn OFF the main Arp On/Off button.

Remember, incoming MIDI data can trigger the Arpeggiators. In addition to being able to trigger Arps with the keyboard, incoming MIDI data can control the Arpeggiators as well. This is a big feature. But the significance is: if you want to play MIDI data IN to the Montage, (as when just playing back) without them responding, you must bypass the Arpeggiators.

Hold [SHIFT] + [ARP ON/OFF] - this temporarily disarms the eight Arpeggiators and is designed to facilitate your situation.
The Arp On/Off light flashes to denote you've temporarily bypassed the Arp function.

Well, if the montage kept playing arps...but its´not, it´s playing one drumsound per 10 seconds. This is not a tempo I have set up anywhere at any time in my software. That´s why I wonder where the hell this is coming from.

At this point the only trick to keep working on my project was to record the drum arps as a song inside the montage, import the song and slice it up into arps and work on those.

I´ve been playing with the midi setup for at least 3 months now and still not working consistently. Honestly, the superknob, motion sequences, even fmx editing, well... everything about the montage is childs play compared to midi recording in sync for me. I expected it to be the other way around - since I´ve never assigned functions to knobs before but have been recording to daw for a decade...

But you will have to admit, no matter how long you've been recording MIDI, you probably were not recording multiple MIDI Channels and multiple Arpeggiators. Sorry, I didn't finish the point I was making above... when you have MIDI SYNC set to MIDI, the Montage is typically waiting for clock commands but it can also run on its own clock.

The cause cannot necessarily be definitively diagnosed from here but you may have a situation where the clock sync signal is traveling in a loop. No matter how briefly this can cause a random hit. So,ply reset the Arp On/Off Switch, to rearm it. A clock loop could manifest itself with an intermittent discharge. Or if it is running at a multiple or exact subdivision of the tempo, that is total possible through Knob offsets. (Unit Multiply)

The Montage can "reference" the external clock source and can operate at multiples or sub-divisions of that master tempo. That's programmable.

no I was never recording multiple midi channels and arps but right now I cannot even record a single one in sync with cubase. I just can´t get it to sync with cubase. what do you have to click here (attached image)? it worked last week - now absolutely impossible to get it synced, I´m not even talking about recording an arp yet - I want to see the bmp of the montage adapt to that of my daw project. what a nightmare.

cubase set to midi montage 1 in out all channels, montage set to record arp, midi clock to midi, as usual.

oh, so now after a break and a reboot, suddenly sync works again.
but this is no good if it´s not consistent.
I can´t spend an eternity on sync problems before each recording session or I will stop wanting to record pretty soon.
this thing has to work consistently and instantly and I don´t understand why it doesn´t. and why so many daw forums are full of people desperate with midi clock issues.

Sync problems can occur, even a brief, oops, when routing can send clock in a circle (loop). And this can spell trouble. A good practice, and most folks who engineer with computer-based system have a similar workflow, if you need to stop, rewind, or momentarily leave a mode/situation where items need to be sync'd... you get in the habit of quickly disarming and then rearming the slave side device, the Arps in your case. When you have a master clock device and a slave, you must optimize their communication.

MIDI clock works like a gear system... if the master clock is sending clock during stop, and if the receiving device is using a setting where it can start independently, you must get used to the fact that a clock tick here or there may slip. Depending on exactly when you stop the master, the slave could be a tick behind.

Here's how this can happen, you press stop, you do so inbetween pulses. In order to restart things in-sync, it is simply wise to Return to Top on the Master and toggle the Slave devices, Arp or MS, On/Off so they both reset to the "upper left corner of the page" (a musician's expression here for restarting/resetting everything to the very tip top of the phrase.

MIDI clock is rather coarse, but it's tight enough, once you get it running properly, and if you remember to reset master and slave. It's just a good habit.

Also remember the Master's Start and Start and Continue commands are completely lost on Arpeggios and Motion Sequences, because even though they Reference the master clock, they Start and STOP according to when you interact with the keyboard. Another reason, to always disarm and rearm the slave clocked device, what if the last time you ran a take you were 5 ticks off. Resetting your slave device is simply GOOD PRACTICE.

Hope that helps.

turns out the Montage makes the crazy drumming sounds by itself every 10 seconds without me even ever opening Cubase! Just being connected to the computer makes it play. I guess I´m gonna be busy for the next few years with this.

this is not the only problem by far, I also can only edit notes at random. I am on one track, recording 2 takes, one after the other, with the exact same settings. on take 1 I can edit the midi notes, meaning I hear the corrected notes. part 2, I move notes around and they stay mute. Only the original notes sound, no corrections possible. I cannot hear anything when I try to draw in notes either. wow, this is beyond awful.

and when you say turn off the arp button on the montage when playing back the recording: as soon as I push play in cubase this turns on the arp button on the montage, no matter how many times I turn it off, it does not stay off at playback. I really can´t figure ANY of this out.

I imagine when you connect the Montage to the PC - without Cubase, you would have no MIDI sent to Montage. I wonder if the drum sounds are being delivered over the audio path ("soundcard"). You should be able to mute the audio send to Montage.

I would also take a look at what a MIDI diagnostic tool (like MIDI-OX for the PC) has in terms of MIDI traffic around the event of the periodic drum sound. That would cover, for me, a form of diagnosis for the drum event from both possibilities assuming external control.

There's also internal control to ponder with a short list (song in the recorder playing back - although that's obvious due to the mode switch to recorder), ARP firing off, etc. But that's off-script of the PC having much to do with it.