Reaper – Midi Clock Sync – Success!

For  a while now I have been trying without success to get three external sequencers to sync with Reaper.

Korg EA-1, Korg Es-1 and Roland M-303

Using midi options and options.

Screen Shot 2014-10-09 at 12.21.38 Screen Shot 2014-10-09 at 12.21.58

Screen Shot 2014-10-09 at 12.20.30

Whilst It works to a degree it isn’t ideal – timing is off and looping is out of the question.

If you press play from the start of a project they will all fire along nicely – record it though and they will be out by what I can tell is a 32nd.

Not good.

So I looked around and found this thread.

In the first post the poster mbncp has a link in his signature to MidiClock.txt

You will need to download this to your reaper plugin folder and change the extension from txt to js.

A different method would be to open the txt file and copy all the txt and do the following.

Screen Shot 2014-10-09 at 12.33.37

Open FX –  ‘Add’ right click and ‘Create new JS FX’

Screen Shot 2014-10-09 at 12.34.00

Name it something – probably best to call it ‘MidiClock’

Screen Shot 2014-10-09 at 12.34.20

Click ‘Edit’

Screen Shot 2014-10-09 at 12.34.39

The following screen will open – this is where we will post our code.

Screen Shot 2014-10-09 at 12.35.00

Open your ‘MidiClock.txt’ file and copy all the text.

Screen Shot 2014-10-09 at 12.35.35

Now go back to Reaper and the opened FX.

Select all of the code and paste the new code from the txt file.

Screen Shot 2014-10-09 at 12.35.52

You should now see this.

Screen Shot 2014-10-09 at 12.36.02

I’m not sure but I think you need to click ‘Full recompile/reset’ to enable save.

Screen Shot 2014-10-09 at 12.36.20

Either way if you close the ‘Edit’ window it will ask you to save what you have done.

Screen Shot 2014-10-09 at 12.36.30

I then removed the finished plugin and then added it back to get it to launch as it is below.

Screen Shot 2014-10-09 at 12.37.24

The next thing to do is make sure your midi device is set to send SPP out.

After that we need to set up a track to send the next fx to our external device.

On the track containing your ‘new’ midi clock.js

Click the ‘io’ button

Screen Shot 2014-10-09 at 13.01.35

Screen Shot 2014-10-09 at 13.01.15


Look at the ‘MIDI Hardware Output’ section

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We need to change this.

Screen Shot 2014-10-09 at 13.05.22

The ‘Output’ should match the midi device that your external device is connected to.

In my case the Korg ES-1 is connected to my Focusrite Pro1010

Now here is the important bit, midi in on the ES-1 is set by default to channel 11 – if this is not changed here to match midi sync will not work.

Now with this setup I have perfect syncing and I can loop sync as well.

Not only that, if I connect my EA-1 via midi thru and then my Roland MC-303 to the midi thru of the EA-1 I get all three in perfect sync.





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  1. Too bad, didn’t work for me. I had high hopes 🙁

  2. Hi there,

    As an MC-303 owner I’m finding your posts inspiring although I am still unable to solve my problem. I am hoping you could advise?

    My problem is pretty much summed up in another persons post here

    Although my problem is specifically with the MC-303.

    So I think the solution is to allow reaper to tell the MC-303 when to start playing using midi. I have no idea how to do this though and have had no luck following your instructions.

    I am entirely new to reaper although have some experience using cubase. Do you think you could help?



    1. Hi there, unfortunately I don’t have an MC-303 anymore to be able to work this out properly although I can maybe give you some advise?

      First make sure the MC-303 is connected to Reaper via midi device – out goes to in and in goes to out.

      Hold SHIFT and press SYSTEM[keyboard pad 16] to access the System Setting. display.
      Use the SELECT < > cursor buttons to select SY1.
      Use the VALUE dial to choose: int (internal), SLv (Slave) or rEt (Remote) as shown in the NEXT display.
      Press EXIT.

      In Reaper:
      In Preferences – Audio – Midi Devices set up input from Midi Device between MC-303 and Reaper

      Open output device and enable output and enable send clock to this device.

      You should now be able to press play on Reaper and start the MC-303?

      You can then record the midi by creating a track and having the input set from your midi device.

      Like I said not got the unit anymore or any outboard sequencers but I seem to remember this being one way.

      1. Thanks for the reply. I had been connecting in to in and out to out 😂
        I will give this a try and hopefully make progress. 😀

      2. It worked! I’ve been struggling to do that, with various daws and no luck for ages! Thanks so much 😁😁😁

        1. No problem, glad it worked.

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