I haven't tried that with custom arpeggios before, so I can't comment on whether it's possible, nor how to make this work; however it may be possible, as there are 3 different 'Convert Types' to choose from when configuring a custom arp on the Montage:

Normal, Fixed and Org Notes

Fixed would work if you record all the chord changes as one arp; however if you are wanting to use the arp in such a way that when changing chords manually, that it changes to a 7th chord when you press the 4 keys/notes, then maybe there's a way to record it to do both!?
It would require using either Normal or Org Notes instead of Fixed, but hopefully there's a way to record the arp notes to provide options to allow for this. I just haven't experimented enough with it to know what needs to be recorded to make it work.

But my gut tells me to try the 'Org Notes' (Convert Types) option first, as I think that may allow you to be able to play the 7th chords and also play triads as well..!?

thanks for quick answering.

until now I tried booth "Normal and Org Notes". Best Results I get with Org Notes
but there are no 7th chords when recording with triads.
When recording with 7th as I said everything is 7th.
Convert type fixed means it is fix for Drums only I think.
Maybee I have to split before convert my recording into 4 Areas for Am7
for example "A C E G" into 4
tracks so first only A second only C
c and so on.

The "normal" type does not have chord intelligence but will "pass through" the notes you play, whatever they are, and only use the rhythm in the ARP applied to the notes you're holding. Therefore, assuming you're playing a full 7th chord - it'll play that. If you're playing a triad - it'll play that.

You've got to go under the arpeggio settings and change the note range for the arpeggio so trigger notes are only in the range where you hold your chord notes so the arpeggio doesn't try to take your lead line (non chord) and put that into the arpeggio.

an important detail I forget to say I want that the chord intelligent follow my chords right.
with factory Arpeggios special for chords it works. But with my custom built arps not.
Maybe the factory arps have more rights or possibilities as custom ones.
Or maybee Yamaha limited our possibilities and don't won't that custom arps reach the full potential of an factory one.
Who knows what's under the hood maybee there are other hidding conversion type only Yamaha get access to.

Yamaha doesn't provide an arpeggio editor that unlocks the potential of the arpeggiator. "Normal" will play the rhythm of the recorded arpeggio using the notes you are holding on the keyboard. Therefore, you would hold down the notes and the arpeggiator will play each note together using the recorded rhythm.

That doesn't work if you want notes+rhythm to come from the arpeggio in some pattern but change the amount of notes played when you hold down more keys. It only works if you're ok with all of the notes playing together while you hold the notes in the rhythm of the arp.

The more you look into this, the more it will do your head in.

Quit while you're somewhat in front of the coming realisation that Yamaha's done a huge disservice to arpeggios, phrase sequencing, pattern sequencing (and chords and keys), not to mention controller integration within these, too.

Get an iPad app or plugins for your fav DAW to manage your controller and arpeggio needs. This way you'll save huge amounts of time and realise whatever creative goals you want without going a little stir crazy.

Andrew sure your right but I wanted to realize all in one box without needing an DAW

This response is an official statement of some of the limitations of the interface:

https://www.yamahasynth.com/forum/distinction-between-scenes-on-preset-8z-tom-heartz#reply-19609

There's also an old article with a "stay tuned" kind of message that an arpeggio editor may be coming. I think this was a generation or more ago when this was authored (before Montage/MODX).

The main message to capture here is that arpeggios that do an "if-then" when holding more notes are not supported. Something that would be needed to accomplish what you're asking with chord intelligence (Org Note) style but adding different lines depending on 3-vs-4 notes held.

[quotePost id=116024]Andrew sure your right but I wanted to realize all in one box without needing an DAW[/quotePost]

if Arps and simple sequencing are your thing, you might want to consider a second hand one of these to pair with your Montage/MODX, as they are cheap and powerful:

https://youtu.be/bPdvJclTeCg?t=822

And the WaveState's sound chops fill the gap between FM-X and AWM2 almost perfectly. Sounds that are tricky to make with the FM-X or AWM2 engines are the bread and butter of the WaveState

For arp construction and programming, I wish there was a step and/or TR-S style sequencer in the MODX/Montage with logic programming options for note and controller parameter dynamic response to input. But I don't think it will ever happen, despite the obvious onboard capacity to run these things.

Yamaha could, on these things, outdo the sequencers and arps of things like the elektron range, complete with parameter locking/stepping, as it's all in there to do just that.

Yet Yamaha act utterly disinterested in the MODX/Montage potential. It's seemingly served its purpose in a slice of time within the market, holding them off from having to make a decision on what a marquee product of the next wave looks like.

Interestingly, I don't think they are any the wiser as to what to make, so don't expect a replacement for at least another couple of years.