Syncing Rack 2 in a Daw (Reason 11 for example)

Hey all. Sorry if this is a super basic question or if it’s covered elsewhere but how do I sync the stop and start of a DAW with Rack 2?

Specifically I would like Impromptu’s Clocked to sync to Reason 11’s play and stop but I’m sure there are other ways I’d like to sync up the play heads of DAW’s to modules in Rack but for the life of me I can’t figure out how. Seems like a VST is sort of pointless if I can’t figure this one out :slight_smile:

Welcome, @MostlyMinerals! Interesting question–I’ll experiment later with this. What exactly do you want a copy of the DAW clock in Rack for (versus just driving Rack with externally clocked MIDI events)? (I mean, there are lots of potential reasons, but it might help to know what your immediate goal for it is).

Keep an eye out for @Omri_Cohen 's videos, he apparently has a whole VCV VST series coming up soon.


Thanks - Well since my DAW of choice is Logic I am running Rack 2 in Reason and it is not clear how to get midi clock from Reason into Rack either. Basically I want to get my patch to begin playing when I hit play in Reason.

Im sure this has an incredibly obvious solution but this isn’t my normal workflow as I mentioned.

Psyched to see what Omri has cooking!

You use the Midi > CV module. The CLK out gives a 24 ppqn pulse from the DAW. Plug that into Clocked’s BPM input and press Mode+ on Clocked until it says P24.

It should then sync and start/stop automatically when you press play/stop in the DAW but you could also take the CONT and STOP outputs from Midi > CV, put them both into an OR logic gate (or Bogaudio uMix works too) and plug the output of that into Clocked’s Run input (technically the start/stop may be slightly more responsive if you do this but the difference is relatively small)


nice! Expertise in action :slight_smile:


POW! Works like a charm!

I appreciate you

~ josh

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Great stuff. I was missing the ‘P24’ setting and couldn’t work out why it wasn’t synching. All fixed. I can carry on now. Thanks. J

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Excellent tip. Thank you!

Hey! is it possible with the free version as well? Thanks

Is there any way that Clocked could realize that it’s in this situation and an least show a warning? This question is asked so often…

VCV free version doesn‘t run as VST inside your DAW; nevertheless you can still sinc it via midi or audio in standalone mode.

Cheers, dDom

Yes - you would need some method of generating an audio clock pulse in the DAW (such as the Silent Way Sync plugin) and a way of sending audio back and forth between your DAW and Rack. It’s a bit of a PITA but it can be done. Rack Pro makes all this much simpler.

It can also be done with midi but due to jitter the sync is not very tight.

After chatting with Steve about the idea, we decided it could actually just automatically switch to P24 if, when in BPM CV mode it detects two rapid pulses on the BPM input. This can be tested, if you (or anyone that builds plugins) can pull Impromptu and try this latest version, any testing will be much appreciated! If this works well, it will definitely reduce the number of times newer users get stuck on this :slight_smile:


With the latest commit Marc has made, if you just connect the CLK out from Midi > CV to the BPM input of Clocked, it will detect the fact it is receiving a clock pulse rather than BPM CV and will change mode automatically to P24 - which should hopefully put an end to most of the “how do I sync the Rack VST” issues. Now it should ‘just work’.

To be clear, this automatic change to P24 will only happen when the module detects clock pulses at the BPM input when it is in the default BPM CV mode. If the mode has already been changed to another P value like P12 for example, no change will happen.

It seems to behave well with my initial testing but given how widely used this module is we could definitely do with some more testers throwing it some curve balls to see if there are any potential issues before releasing it.



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Thank you for the change!

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Awesome to about recent update.

Related question, what’s the best way to fix the sync issue when a sequence starts up? I use Impromptu Clocked as primary but whenever a sequence starts, the first three notes or so are out of sync. You can hear this if you are clocking VST FX using Host. But after this, the sync is fine.

I think one trick might be to just temporarily expose Clocked to the correct external clock before you start the performance, such that it learns the intended BPM, and then when you restart it, it will assume the same BPM until the next pulses arrive, so in theory that should help.

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FX with a sync input take some time of their own to figure out the tempo - and given the clock you are sending them is often just 1ppqn, they will take significantly longer to figure out the correct tempo than Clocked does with a 24ppqn input. This is because tempo is calculated by measuring the time between pulses - the lower the ppqn, the fewer pulses there are (for a given time) and the longer it will therefore take to calculate the tempo.

Also, unlike Clocked, those FX may not ‘remember’ the previous tempo when you stop then run again.

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This is of course why in the (now ancient) MIDI spec the clock ran all the time, and did not shut off when a device “stopped”. In these VST applications is it also easy to accomplish this, or does it need to be done as a kind of “hack” by the user?

Unrelated - can you “tell” Clocked what the expected tempo is to it can start immediately, and stay in sync if, in fact, the MIDI clock tempo is close to the one you tell Clocked?

Unrelated - have you ever used the “nord” protocol for reset, as an alternative to the “send it at the same time as the clock but ignore clocks for a millisecond afterwards” protocol? In my (unreleased) Arpeggiator I gave a choice of both, but the default was the Nord reset, since that protocol (to me) is unambiguous and always works.

It would be great it you (or someone) would write up a guide to syncing in VST, since there is so much confusion about this. I’d even say that VCV should link to such an article, but afaik they never link to external info.

Also, glad you got some thanks for the change,

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