Before diving into the Boss DB90's manual - I want to be absolutely sure you need it. Aside from some extra features it may present - I'm sure there are many - you expressed the reason why you're using an external metronome is primarily due to an inability to assign a click to a sequencer.

Sequencers can come in different forms - maybe you have a MIDI sequencer that is not USB based and not PC/Mac based. In this case, what I'm about to say is not necessarily going to help since you require an additional analog channel in this application. In which case I'm not going to say to stop using what you are and buy a digital rig to replace it.

However, if your sequencer is computer based - your click track inside MODX is able to be routed to any USB channel, Main L&R is the default - but it can be changed. With a sequencer inside a computer - the click track can go to any of the several digital USB channels while your audio data goes to a different set.

Now on with your original question ...

According the DB90 manual, the device can only be synced while in "MIDI mode". The only way to sync the DB90 is use of start/stop messages. DB90 does not advertise doing anything with note on/note off messages. MODX can send start/stop messages by pressing the transport buttons when so configured. Transport controls do not kick off ARPs - so this may be tricky to press both the "play" button and a note on the keyboard at the same time. Start/Stop can be used to start and stop playback of a MIDI file (with option to turn loop on) - so that may be able to replace your ARP. Re-configure as a MIDI file. Therefore, you sync up your DB90 and automated playback at the same time.

The only other thing I can think of is to stick a computer or device between which will translate a midi-note-on event into a "start" command. MIDI Start is 0xFA, stop is 0xFC. As long as repeated starts do not mess up DB90 - it should just start with the first note press (or pick a single key you wouldn't normally play - yet also starts your ARP). Then perhaps you can figure out something else to translate to stop - a different key. Inserting a computer or other capable hardware between gives lots of options.

Hi Jason,

thank you for your reply. It started me thinking about other possibilities. I use the arpeggios during live performing. The click is necessary for the band (drummer) to keep the time. I don't want to bring my computer to the stage. I checked if the metronome (boss) will start when I hit the play button on the sequence and that works. Now I came up with the idea to make a midi file or sequens in the modx so I can hit the play button and the metronome will start BUT: when I hit a key (with a arp on it) the arp is not in sync if I don't push the key 100% on the beat, is there an option to make the arp in sync with the sequens or midi file on the modx, I think the problem will be solved than.

Regards Erik

Starting an Arpeggio is done by triggering a Note-On at the Velocity and within the Note Range specified to control the Arpeggiator. Like playing normally, the timing of that Note-On event is the responsibility of the performer. This is always going to be the case.

It should be mentioned that the MONTAGE has Assignable Outputs, to which you can assign the Click specifically for what you are attempting to do (this can be sent to a monitoring system for the entire band to follow). The MODX does not have the separate Assignable Outputs. (But there should be no expectation of KEY-ON START transferring the start of clock between devices). You can approach this “conductor” issue from the opposite direction...

What you can do
What you can do is take the Audio Output of the external metronome and connect it to the AD INPUT on your MODX.
Set the MODX’s “MIDI Sync” = AD IN

Now you can use the Audio Output of the DB90 (I’m assuming it has audio Outputs) to provide tempo for all tempo driven functions within the MODX. This includes Arpeggiators, Song playback, Tempo driven LFOs, Motion Sequences, Effect processors within the Motion. Control Synthesis Engine.
You can use a signal splitter to simultaneously deliver the audio click to some kind of monitoring system for other members to hear. (I’m a big believer in all members of the band being able to follow the “conductor”).

Now as long as you all know how many clicks are to be used a Count-in, you now can use the DB90 as the band’s tempo conductor. Start all songs using it. Two measures for nothing is the most common count-in.

Your MODX will follow the audio click... you will still need to play “on time” (triggering notes at the appropriate timing is always going to be your responsibility) If you are late, the Arp Phrase will be shifted late. Say you miss the downbeat by 20 clock ticks, the entire Arp Phrase will be clock shifted 20 ticks late. If you are early the Arp Phrase will be ahead of the beat... unless you:

Use the Arp parameter, SYNC QUANTIZE to quantize Arp Phrase start time. This quantize works on the start of Arpeggio Phrases.

Thanks for all the help but I got it fixed 😀 Thanks to the things Jason mentioned . What I did:

I recorded an empty sequens part for 1 bar
set that on loop
set arpeggiator to quantize or sync on quarter beat
did some tweaking on the utility page with the midi settings (don't know what I did but it works)

Now I start the sequence with the start button
Boss DB starts to play the click
now i can trigger the arp and it is in time because of the quantize to bar option.

Thanks and I hope someone else can iso this trick

Regards Erik

Glad I could help. Yes, the timing of when an arpeggio starts is always the responsibility of the keyboardist. It's not difficult to start arpeggios at the "wrong" time relative to when you'd prefer and get an undesirable result. Glad you could find reasonable guardrails to help facilitate this critical timing requirement.