MIDI Clock Havoc

All the years I’ve been using Cubase, I’ve never been able to get MIDI Clock to behave properly throughout my rig without setting up special MIDI filters in my MIDI interface.

I have some hardware synths that I’d like to send MIDI Clock to in order to synchronize the arppegiators to the tempo of my Cubase project. I go to the Project Synchronization Setup, go to the MIDI Clock Destinations tab and select the device I want to receive MIDI Clock. That’s great. The synth arpeggiator syncs with Cubase, but my drum machine takes off too when I never selected that device from the Project Synchronization Setup to begin with.

Another oddity is that if I select a second synth in the Project Synchronization Setup, then the arpeggiators goes twice as fast. Select a third and it goes 3x as fast.

Cubase is sending realtime MIDI messages across the entire system and there doesn’t seem to be a way to control this properly from the Synchronization Setup and it seems like it should work… select the device(s) you want and just go for it. This article in SOS magazine seems to suggest the same…
https://www.soundonsound.com/techniques/cubase-synchronisation-options

Now, to get past this, I have to go into my MIDI interface setup software (MOTU Clockworks) and filter out the MIDI Realtime messages since I can’t seem to figure out how to get Cubase to do it. I can filter out the Realtime messages on the ports that I don’t want to receive MIDI Clock through MOTU Clockworks.

The problem is, I am going to have to replace this interface as it’s now past it’s prime. Plus, even if I kept it, I wouldn’t be able to use Clockworks after I finally update my OS to Catalina (32 bit software won’t work). I have my eye on a new interface from ESI that is class-compliant and requires no drivers, but you can’t customize your own setup. So I need to get the filtering to work from within Cubase.

Any suggestions are greatly appreciated.