Plugin Parameter Modulation in Reaper

There's been a steady growth in acceptance for Reaper as a serious DAW, thanks to its feature set. In this tutorial Gary Hiebner explores the finer points of plug-in parameter modulation in Reaper.  

Reaper is filled with lots of handy features that sit around in its assortment of menus. And one of these is Plug-in Parameter Modulation. This allows you to modulate a parameter on any of your plugins. This gives you great control over your tracks and plugins, plus allows you to add movement and interest to your tracks through the modulation. Let's see how this is done.

Step 1 – Choose an Effect

On a track, click on the FX button to bring up the Add FX dialog box. Choose a plug-in to add to the track. I'm going to be using the ReaEQ. But you can add any plug-in and follow along.

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On the EQ, set the first band to a high-shelf. Set the Frequency to about 15 kHz and the Gain to -34dB. Set the bandwidth to about 0.17. Also give a slight boost with band 4.

I would like the band 1 Frequency to sweep up and down the frequency range to create a filter effect. This can be done with Parameter Modulation.

Step 2 – Enabling Parameter Modulation

On your track click on the Trim button. Scroll down to the effect you want to modulate. I'll be working with the 1st frequency band with the ReaEQ. So on the 1-Freq (High), tick the Mod box. 

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This will bring up the Parameter Modulation dialog box. By default the Enable parameter modulation is ticked. This will determine the baseline amount of modulation that is applied. 

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Let's first test this out using an Audio Control signal as a modulation source.

Step 3 – Using the Audio Control Signal

With Audio Control signal ticked, go under the track audio channel and choose 1+2. I'll be using these as the audio track source, you can set it to other tracks. Leave the direction set to positive, but you do have the option to change the direction to negative and centered.

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The right display box will show you how much audio control signal modulation is applied. Using your mouse you can change the shape of the audio signal, hence changing the way the audio control modulation is applied.

Play back your track and start bringing up the baseline to about 80%. Set the attack to 227 ms and the Release to 290 ms. Bring the Min Volume down to -42 dB. You will now see some modulation happening in the Audio control signal shaping window. The green lines represent the modulation changes. Now bring the baseline down to about 50%. You will hear more modulation occurring. Drop it down to 20% and even more modulation occurs. Tweak the Min and Max Volume settings, these will change the modulation control over the frequency parameter. If you view the ReaEQ while the track is playing back, you will see on the plug-in how the parameter is being modulation. So as a suggestion, have the plugin UI and the Parameter Modulation window open at the same time so you can see how the parameter is being affected.

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Step 4 – Using the LFO

Now let's test out the LFO in The Parameter Modulation window. Untick the Audio Control Signal and now tick the LFO. This low frequency oscillator will now modulate the ReaEQ high-shelf band. You can choose a different waveshape. 

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Try these out. I'll stick with the Sine waveshape as it applies smooth modulation transitions. The random waveshape works really nice to introduce randomization into your modulation and sound sources. The speed of the LFO is in Hz, or you can change it to sync to the tempo (by ticking the Tempo Sync box). This will be now measured in beats. So 0.5 will be at half the beat, 0.25 at a quarter of the tempo, and so on…

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The strength will determine how much of the LFO is applied, and the direction can be changed as well.

Step 5 – Multiple Modulation

The beauty with this Parameter Modulation box is that you can apply both the audio control signal and LFO to a parameter at the same time. And with each one, you can dial in a different setting, so there are many ways to modulate a parameter. And that's only on one single parameter. 

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Through the Trim box, you can go in and add different forms of modulation onto each parameter. This gives you great control over the modulation.


Go in and build up your effects chains on your track, and then start assigning modulation parameters to these plug-ins. The possibilities are endless. You can really go wild with this to create some unique sounds plug-in effects on your audio using the audio control signal and LFO tools. They can be used to create movement in your tracks, which might not have otherwise been possible through the plugins or through automation. Try this out in your next Reaper tracks. You might surprise yourself.

Take a look at the following tutorials to get further techniques with Reaper:

Reaper 101: Introduction to Reaper

Reaper 102: Working With Audio

Reaper 103: MIDI, Instruments and Plugins

Reaper 104: Mixing and Automation

Gary Hiebner is an enthusiastic South African Sound Designer and Apple Tech Head! Gary has been involved in the South African music industry for the decade, and in this time has also been involved in the sound design and music production for many advertising agencies and media houses. Gary is a devoted Logic and Ableton user, but he al... Read More


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