Sidechaining with ReaComp

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Side-chaining with ReaComp[edit]

What Is Side-Chaining?[edit]

In essence, a side chain is where you use the output of one track to control the output on another track. You could use Sidechaining if you want to have your background music on one track automatically lowered in volume, or ducked, when there is speech on another track. So for example your podcast intro music is ducked when you start speaking.

How To Set Up A Side-chain[edit]

In the side- chain we will be setting up in this tutorial, we will be sending the audio from our vocal track to the music track. We will still want the vocal track to go straight to the master track so we can hear it. The copy that is sent to the music track will not be heard in the master, however it will be used to compress the volume of the music, or in other words, to duck the music.

First, create two tracks. In this example, track one will be called music, and track 2 will be called voice. This article assumes that you already know how to create tracks. If not, then read this article to learn how.

Now we have a track with music, and a track with voice. The first step is to change the music track from a standard 2 channel stereo track to a 4 channel track. The first two channels are your standard left and right channels, channel 3 and 4 will be auxiliary channels, meaning that you won't hear the audio being sent to those channels. To change the track to a four channel track, press I on the music track, to open the routing dialogue. Tab until you hear, “track channels.” Press Alt+Down arrow keys to open the combo box so you can select the number of channels. Arrow down to change from 2 channels to four channels. Press Enter to consolidate the change. Then press escape to exit the routing dialogue.

Next, setup a send, so that the audio from the vocal track is being sent to the music track. You can press I on the vocal track to enter the routing dialogue, tab til you hear, “add send.” Press Alt+Down arrow keys to open the combo box to select the destination track. Arrow down to get to your music track. When you're there, press Enter for the send to add, then press escape to leave the routing dialogue. Your send has now been added.

Next, set the destination of the send from the vocal track to the third and fourth channel of the music tracks. This will send the audio from the vocal track to the auxiliary channels of your music track. This means that the audio on your vocal track is being heard through your vocal track, but is also being sent to the auxiliary channels of your music track, so that you can use it to influence the music track.

To send the vocal track to channels 3 and 4 of the music track, press I on the vocal track. Tab until you hear, “send to track one, music, delete button.” Once there, invoke your contextual menu with either the Applications key or the Shift+f10 combination. Use the down arrow key to get to the "Destination Audio Channel" setting. Press enter on that setting and, once again, make use of the down arrow keys to get to the 3/4 option, which will likely be the third option in most of the cases. Press the Enter key to consolidate the change and then press the Escape key until you land in the main Reaper window.

Now, we can add a compressor to our music track. In this tutorial, we are using the included compressor, Reacomp. Press F on the Music track to open the FX dialogue. Add ReaComp.

Once added, tab through the settings of ReaComp until you get to “detector input.” Set the detector input of ReaComp to aux 3/4. This means the compressor will be influenced by the audio being sent to it on channels 3 and 4, in this case, the audio from your voice track.

Finally, we need to set up the compressor suitably to compress the music enough to hear the voice over. Set the ratio to a suitable value, perhaps 4/1 or higher. You can use the precomp and attack parameters to affect how quickly the audio is ducked and the release parameter to affect how quickly the audio returns to it’s original volume once the voice over stops. The lower you set the threshold, the quieter the music will be while it is being compressed.


We have now set up a side chain to duck our music while speaking. This may seem fairly complex at first, however understanding the concepts covered will help with lots of tasks you might want to undertake in Reaper, or any professional DAW

Some Tips for Windows and Mac users[edit]

As with most things in Reaper, there are many ways of doing things, and the best way may be different between platforms. For example, in Windows, you can set up a send as described above from the "View I/O for current track"dialog by pressing "I" on the track. Alternatively you can use the alt plus applications key on the track and you will find the options buried in these menus. Once you have a send set up, when in the I/O for current track dialog, you will find a delete button for the send. pressing the applications key on this button will bring up further options for configuring the send.

Setting up a send from track 1 to track 2, is exactly the same as setting up a receive on track 2 from track 1.

When on the Mac, the most efficient way of setting up the routing for the side-chain is to follow the below steps.

  • Bring up the I/O for the Music track
  • Change the Track channels: from 2 to 4
  • Keep navigating through the dialog to the "Add new receive..." pop up button and add a receive from the Voice Track
  • navigate to the Destination audio channel selection box, and change from channel 1/2 to 3/4

The routing is now set up and you can now close the dialog and add ReaComp to the Music track.

Audio Tutorials[edit]

There are two tutorials on side-chaining, one based on MacOS and the other based on Windows. In the MacOS audio tutorial, Garth Humphrey's talks you through creating a side chain in Reaper with ReaComp. Download the mac audio tutorial here.

In Windows, Daniel Montalvo shows us how to accomplish side-chaining on Windows. He uses JAWS for Windows but he also explains what the differences are when somebody is using NVDA. Download the Windows tutorial here