Tutorial: Using Auto LFO to Control a VST Effect Parameter

Making a MIDI effect like Auto LFO control a parameter in a MIDI-enabled VST effect like FabFilter Pro-Q3 is painfully underdocumented, and even after I got it to work, I still feel it’s a rather tortuous procedure. Therefore, even though I explain it here, I still place this post in the “Feature Requests and Suggestions” section: please Steinberg, document this feature better and provide some examples. And, if possible, make it more straightforward.

This example uses controller 1 (modulation) to control the frequency of a band within Pro-Q3.

There are two ways to go about this:

  • Use a MIDI keyboard with modulation wheel to make Pro Q3 learn what controller to listen to, and only then connect Auto LFO to Pro-Q3.


  • If you do not have a MIDI keyboard you can accomplish everything using just Auto LFO. As soon as you insert Auto LFO on a MIDI track it will start emitting controller events (after all it’s an LFO), and these will swamp Pro-Q3 the moment you activate its MIDI Learn mode. This method almost always works. However, I did once got the dreaded “A serious problem has occurred” message, and I suspect it’s because Pro-Q is caught unawares by the controller messages pouring in from Auto LFO.

Use a MIDI keyboard for the MIDI Learn phase, and only then connect Auto LFO

  • Insert Pro-Q3 on the audio track you want process.


  • Create a band in Pro-Q3.


  • Create a MIDI track and set its output to the Pro-Q instance you just created.


  • Open Pro-Q3 again.


  • With Pro-Q3 open, select the MIDI track you just created. Important! Otherwise the MIDI events we are about to generate won’t reach Pro-Q3.


  • In Pro-Q3 click MIDI Learn along the bottom of the plugin interface.


  • Click the green dot of the frequency band on the yellow line and click the Frequency knob of the band you just created. These two actions make Pro-Q3 understand that you want to control the frequency of the first band.


  • Move the modulation wheel. Possibly after a little hick-up Pro-Q3 now knows (and shows) that the frequency of band 1 is controlled by the modulation wheel (controller 1).


  • Hit the Close button that appeared in the top right of the Pro-Q3 panel when you activated MIDI Learn.


  • Now we can insert Auto LFO on the MIDI track. Set its Controller Type parameter to 1 (modulation) and set the other parameters as you like.


  • You should now see the frequency band in Pro-Q3 go frantically up and down.

Using only Auto LFO

  • Insert Pro-Q3 on the audio track you want process.


  • Create a band in Pro-Q3.


  • Create a MIDI track and set its output to the Pro-Q instance you just created.


  • Insert Auto LFO on the MIDI track. Set its Controller Type parameter to 1 (modulation) and set the other parameters as you like.


  • In Pro-Q3 click MIDI Learn along the bottom of the plugin interface. Even though you don’t do anything yourself, Pro-Q3 is now immediately swamped with control 1 messages from Auto LFO.


  • Click the green dot of the frequency band on the yellow line and click the Frequency knob of the band you just created. These two actions make Pro-Q3 understand that you want to control the frequency of the first band.


  • Hit the Close button that appeared in the top right of the Pro-Q3 panel when you activated MIDI Learn.


  • Possibly after a hick-up, you should now see the frequency band in Pro-Q3 go frantically up and down.
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