Sidechaining is a common technique used in music production to achieve better mixes. Let’s learn how to do it in REAPER and understand routing along the way!
While mixing, you’ve probably noticed that a couple of your instruments sometimes clash, resulting in phase cancellation or muddy peaks of certain frequencies. It typically occurs in the low end of the frequency spectrum since our ears can separate the lower frequencies better. So, the most common clashing instruments are the kick drum and bass.
…but how does sidechaining come into this issue?
What Is Sidechaining?
Sidechaining means using one track’s audio signal to process another track. The signal might include both the transients and frequency spectrum. For example, sidechaining a compressor results in gain reduction when the second track plays. Some even let you specify the frequency spectrum range to analyze.
Using a compressor on a synth or bass track and sidechaining the kick drum turns down the synth’s volume every time the kick drum plays, preventing clashes between the two. Excessive sidechain compression produces a “ducking” sound effect, bread-and-butter for electronic dance music. So, I’ll also show you how to achieve this effect without sidechaining to have an alternative.
3 Ways To Sidechain In REAPER
In REAPER, sidechaining involves creating a send from the source track to the destination track. If you want to make your synth track duck when the kick drum plays, you’ll create a send from the kick to the synth. Then, you’ll select the appropriate plugin for your intention and assign the sidechain. Hence, I’ll first cover how to create a send.
Sends, Routing, & Channels
Creating a “send” transmits the audio signal from the source track to the destination track while still playing the source track via the master channel. So, if you created a send in REAPER, two tracks would play the same audio, resulting in twice the loudness. Conversely, if you created a send and disconnected the source track from the master channel, only the destination/send track would play the audio signal. Such a send track is often called a bus.
REAPER allows you to create a send between any two tracks and send both audio and MIDI data. We can use either a send or bus for sidechaining, depending on whether we want to hear the source track (kick drum) or not. Similarly, we can sidechain multiple tracks using a bus or individual sends. The latter offers more control but consumes more time and CPU resources.
Furthermore, each track in REAPER supports up to 64 channels. A typical stereo track uses two channels (1/2), whereas a mono track uses a single channel. When creating a send for sidechaining, you have to send to the receiving track’s channels 3/4.
Now that we’ve gone through the basics let’s understand the process. Like anything in REAPER, the DAW offers multiple ways to create a send. So, I’ll cover two that I find the most practical and fast:
Drag & Drop
Use this method when the two tracks are visible on your arrangement page or the mixer without scrolling too far. It’s the easiest way to create sends in REAPER.
- Ensure the “Route” button is available on your track control panel (TCP). If you can’t find it, go to Options > Themes > Theme Adjuster and navigate to the “Track Control Panel” tab. Find “Routing” and remove “Hide” in its row.
- Drag the Route button from your source track (kick drum) to the destination track (synth, bass). You can do it on either the TCP or the MCP.
- Alternatively, we can use the mixer. First, ensure the mixer shows the FX inserts and sends lists. By default, they are right above the pan and the FX button. So, if you can’t find the lists, place your mouse cursor at the top of the MCP, which turns your cursor into a two-way arrow, and drag it down. You’ll find the sends list below the FX inserts list.
- Click and drag from the sends list of your source track to the destination track, as shown below:
- Holding Shift while you drag from the sends list or Route button allows you to send one source track to all selected destination tracks. You can use it when you want to create sidechains on multiple tracks. Likewise, you can send all selected source tracks to a destination track.
- When you finish dragging, a send window will pop up, showing you the volume, pan, and other information of the send. Click the MIDI source drop-down menu (left one) on this window and select None. Hence, the send will now only send audio and no MIDI.
- In the Audio destination drop-down menu (right one), find “New channels on receiving track” and select 3/4. Doing so will add a new pair of channels to the receiving track, where it will send the source’s audio signal.
Use this method when your source and destination tracks are too far apart to be visible on your screen without scrolling.
- Click on the Route button or right-click the volume fader of the source track to open its Routing options.
- Under the Sends sections, click on the “Add new send…” drop-down menu.
- Find and click your destination track on the list.
- The send window should pop up. As we did in the previous method, disable the MIDI send and assign channels 3/4 on the receiving track for sidechaining.
Note: You can easily open the send window by clicking on the send on the sends list of your mixer, clicking on the Route button, or right-clicking on the volume fader. You can also use the Receives section instead of the Sends section but do so from the destination track’s routing options.
Plugins For Sidechaining
After you’ve set up the sends, it’s time to select the right plugin for sidechaining. REAPER features several that can sidechain. So, let’s go through some of them.
ReaComp is REAPER’s stock compressor, which is transparent and lightweight. Using it for sidechaining should be the most familiar method for experienced music producers. However, let’s go through the steps:
- After you’ve created your send, add ReaComp to your receiving/destination track.
- Select “Auxiliary Inputs” from the “Detector input” drop-down menu. In REAPER, the auxiliary inputs are typically the channels 3/4, which are the ones we selected in the send menu earlier. However, if you’re using some other channels, please refer to the pin connector section towards the end of this article.
- You’ll see ReaComp’s input meter showing the source track’s signal.
- Drag down the Threshold slider until it goes below the signal.
- Turn up the Ratio to start compression.
- The low-pass and high-pass filters allow you to adjust the frequency range of the input detector. For example, try setting the high-pass at 20 Hz and lowering the low-pass if you’re trying to detect the kick drum alone from an instrumental track. Likewise, you can hone in on the vocals of a podcast to duck the level of instrumentals.
- Adjust the other parameters as required.
ReaGate is a gate plugin, which silences the level of your audio when it goes below the specified threshold. It’s often used to get rid of quiet noises in-between performance. However, ReaGate sports an inverting feature that comes in handy for us.
- Add ReaGate to your destination track, and change the detector input to “Auxiliary Inputs.”
- Activate the “Invert gate (duck)” checkbox at the bottom right corner of the plugin. As the name implies, it makes ReaGate turn down the sound when the signal is louder than the threshold instead of when it’s quiet.
- Turn down the threshold and adjust the other parameters as needed.
- The result can be extreme since ReaGate silences the signal instead of merely lowering it. However, you can turn down the mix knob at the top right of the plugin. Please note that the mix knob is different from the wet and dry sliders.
This plugin is a graphical dynamics processor capable of upward/downward compression and expansion. Simply put, using the freeform graph, General Dynamics can turn down or increase the audio level at any threshold. So, it can result in smooth dynamic adjustments that work perfectly for podcasts or mixing melodic instruments or vocals with other tracks.
The graph displays the input level on the X-axis (horizontal) and the output level on the Y-axis (vertical). Any deviation from the 45° line in the middle of the axes creates a threshold and ratio. So, you can target what processing you want at each signal level. The plugin lets you draw, smoothen, and erase (reset to the default line) the graph.
Here is an example of a compressor graph with a smooth knee:
Following these steps to use General Dynamics for sidechaining:
- Switch the “Detector Input” drop-down menu to “Aux.” Note that using General Dynamics as an upward compressor can result in loud signals.
- I recommend setting the “Detector RMS size” to 5ms. However, feel free to use a larger value, which makes the input detection slower and less sensitive.
- You can leave the Gain Attack and Release at 0, but you should adjust the Input Attack and Release to customize your sound. The Gain Attack and Release alter the compressor’s timing like the attack and release parameters in regular compressors. However, the Input Attack and Release are represented in the graph, making them more intuitive.
REAPER ships with many JS effects, which are programmable and editable inside REAPER. They are typically very lightweight and capable. Furthermore, you’ll find even more JS effects if you install ReaPack.
- Tukan Blue Compressor S2
Blue Compressor S2 is a straightforward but elegant compressor that allows you to switch to sidechain mode with a click of a button. It features a sidechain high-pass filter and knee control. Moreover, you can use the dry/wet knob for parallel compression. The plugin also sports two display types: regular gain meter and scope views.
- Tukan Compressor 3
Compressor 3 is a stereo compressor capable of typical stereo, dual mono, and mid/side mode. I recommend this compressor if you are sidechaining a stereo track with fairly complex imaging with a similar track. Conversely, it might prove too complicated for simple bass-and-kick sidechaining.
- Saike Tight Compressor
Tight Compressor is an incredibly fast and transparent compressor, perfect for catching percussive transients. It’s also CPU resource efficient, making it a great choice for a busy mix. So, I recommend it for most usages if you enjoy tweaking parameters.
- Tukan LA-2Kan S2
Modeled after one of my favorite compressors, the LA-2Kan S2 offers a minimal user interface and a pleasing sound. Like the original LA-2A hardware, this plugin is best suited for smooth results. Hence, I recommend it for smooth ducking effects and silky sidechaining for podcasts and vocals.
Note: Most Tukan plugins feature built-in saturation from hardware emulation. To achieve a clean sound, you can turn it off in the plugin’s options menu.
REAPER allows you to modulate any automatable parameter using built-in modulation tools. These include an audio follower, LFO, and hardware or FX parameter. However, I’ll only cover the first one in this article. We’ll use parameter modulation to modulate a volume fader using a sidechain input as the reference:
- After you’ve created a send, add a plugin with a volume control to the destination track. Not all plugins support smooth modulation, though, and might give subpar results. So, I recommend the “Volume/Pan Smoother v5” JS effect.
- In the plugin, move the volume fader slightly in any direction.
- Click the “Param” button to find the “Parameter modulation/MIDI link.”
- On the window that opens, check “Enable parameter modulation” and “Audio control signal (sidechain).”
- Set the “baseline value” at 50%.
- Change the “Track audio channel” to 3+4 to select the sidechain signal.
- Switch the “Direction” to “Negative” so that the modulator turns down the volume when the signal gets loud.
The graph on the right works similarly to General Dynamics. If you’re confused, try pulling the node in the middle of the graph to the bottom-right corner. Then, move it around slowly to determine the best spot.
If you’re only sidechaining to mix an instrument better and not create an obvious ducking effect, I recommend using an EQ instead of the volume control. I like adding either Tukan’s Orange EQ S2 or ReaEQ. Then, set a peaking band at the clashing frequency and use sidechain parameter modulation to control the band’s gain.
Master Send & Positions
Sometimes, you want the sidechain compression (ducking) to work without the kick drum playing. It’s a fairly common technique in modern music. So, in this section, I’ll show you two options you can tweak to achieve that effect.
First, open the routing options of the source track by clicking on the Route button or right-clicking the volume fader. At the top-left of the routing window, you’ll find the “Master send” option that assigns the master channels to which the signal goes. So, unchecking this checkbox stops sending the signal from your track to the master track completely.
You can use the above method to mute the audio while keeping the sidechain functional quickly. However, since the master send option isn’t automatable, I find the following method more useful:
- Open the routing options of the source track once more.
- You’ll find a drop-down menu that says “Post-Fader (Post-Pan)” by default in each send you’ve created.
- Select “Pre-Fader (Post-FX)” in the drop-down menu. It bypasses the volume fader of your source track, allowing you to automate or adjust the volume without affecting the sidechain. Likewise, you can choose “Pre-Fader (Pre-FX)” as well, but it won’t work for tracks using a MIDI instrument.
- Adjust the volume and pan of the send itself if needed.
Alternative Method (For Pumping Sidechain)
Beyond sidechaining a compressor, you can achieve the same ducking effect on your synths and bass using volume automation. While it may be tedious on many other DAWs, REAPER sports features that make the task straightforward and quick. So, read on to discover how to create the sidechain effect without a sidechain!
- Add the “Volume/Pan Smoother v5” JSFX to your destination track (synth). While you can use the regular volume envelope, I prefer using this plugin for the flexibility of setting it anywhere on the FX chain of my tracks.
- In the plugin, move the Volume fader a little to select it.
- Open the “Param” menu, and click “Show track envelope.” Set a keyboard shortcut to make this step easier. Open Actions (Shift + / or Command + Options + A), search for “Show/hide track envelope for last touched FX parameter,” and add your preferred shortcut at the bottom left of the screen. I use Alt/Option + A.
- The volume fader envelope should now be visible below your track.
- Make sure grid snap is enabled. Then, hold Alt/Option and drag over the envelope to create a new automation item of 1 beat in length. Note that you can use a different length based on your needs.
- Create your sidechain shape. Hold Shift, click to add a new node, and hold Alt/Option to change the curve between two nodes.
- Double-click the automation item to open its properties. Turn on Loop and close the window.
- Right-click the automation, click Save, and give it a name like “Sidechain Duck – 1 Beat.” You can now load this shape into any song or track. To do so, right-click over an envelope, find Automation Items > Load, and click on the name you gave the item.
- Drag the end of the automation item to create looping copies as many as you need.
- Double-click the automation item to open its properties, and adjust the Baseline and Amplitude faders to customize the level and shape as you require.
- If you need to copy the plugin and envelope to another track, right-click the effect plugin, click “Copy FX (include automation),” and paste it to the desired track.
I prefer using this method to control the ducking effect better. Sure, I could create a traditional send and automate the send level. But adding, deleting, splitting (select and press S), and modifying automation items per beat feels way more intuitive to me. So, give it a try, and use each method as per your need!
Pin Connector (Optional Reading)
Typically, you wouldn’t need to learn about the pin connector to create sidechains. It’s mostly for creating multi-channel configurations other than stereo. So, read on if you’re interested in getting a little deeper into REAPER’s routing system!
The pin connector visually represents the input and output channels of a track and plugin. It displays the channels in a matrix, showing how the plugin channels and track channels are connected. Furthermore, the page features the track channel count drop-down menu.
You can access a plugin’s pin connector by clicking the button between Param and UI. It’s labeled with the current channel configuration, which might look like “4 in 2 out” or “2/4 in 2 out.”
You can see “2/4 in 2 out” in the screenshot above. It means the plugin can receive 4 inputs, but only 2 are currently in use (2 out of 4 = 2/4) because the auxiliary inputs aren’t connected. Similarly, the plugin can send 2 outputs, which are both in use (left/right channels).
Once you’ve opened the pin connector, you’ll see two matrices. On both matrices, the vertical array represents the track channels. Conversely, the first matrix’s horizontal array displays the plugin inputs, while the same in the second matrix shows the outputs.
The vertical arrays (plugin inputs) are often labeled by their function. The labels make it easy for us to find the sidechain inputs. For example, take a look at ReaComp’s pin connector below:
You’ll find that the inputs have been labeled “Main Input” and “Auxiliary Input.” The labels may differ between plugins. For instance, Tukan’s Compressor 3 labels them “In” and “SC In.” Similarly, some might not even label them at all, like Saike’s Tight Compressor, which relies on a drop-down menu to display which channels are sidechain inputs.
While most plugins use the same number of channels as the track, some allow you to specify. Hence, the pin connectors of some plugins display the plugin channel count and processing mode. The processing modes include the following:
Plugin Channels: 2
The stereo mode is the most common. It processes a pair of channels, the left and right signals, together. So, if the left channel crossed the threshold of ReaComp, the compressor would compress both the left and right channels equally.
Plugin Channels: 1–64
If you have selected only one plugin channel in the pin connector, the mono mode processes that channel alone. Conversely, the multi-mono is available in any channel configuration. It processes each channel individually, regardless of how many plugin channels you select in the connector.
Plugin Channels: 2–64
This mode regards each pair of plugin channels as a stereo connection. So, if you had six channels, you could pair channels 1/2, 3/4, and 5/6 as stereo pairs. It’s particularly useful for surround mixes or multi-channel bus routing from a multi-timbral instrument in music production.
Plugin Channels: 2–64
As the name suggests, the Multi-Channel mode processes all the available plugin channels together.
Learning to create sends and buses is an important part of sidechaining and mixing in general. You can use them to organize your project and relieve some of the CPU load. So, I hope you’ve found that section of the article helpful.
After you’ve created the send, the question is which plugin to use for sidechaining. ReaComp is the easiest choice and often does the job perfectly. However, I recommend trying out the JS effects like Blue Compressor S2 and LA-2Kan S2. Aside from having a sleek user interface, they might offer a smoother sound.
Of course, you might also prefer the alternative method of automation, my second favorite trick. It avoids puzzling sends and routings and relies on the visual means of envelope automation instead. Furthermore, while I mentioned how you can copy the volume FX to other tracks, you can also create a bus to automate the volume of multiple tracks. However, doing so won’t let you place the volume FX before other track plugins and offers little flexibility.
I often select a method based on how audible the sidechain will be. For example, if I’m compressing an instrumental track to duck it under a podcast recording, I would use a smoother compressor like LA-2Kan S2 or General Dynamics. Conversely, I’d use Tight Compressor if I want to compress some instruments to bring up the bass guitar’s transients. As for the typical EDM ducking, I’d still use LA-2Kan. However, I might switch to automation if I want more flexibility in the sidechain shape.
I hope you enjoyed this detailed guide on sidechaining and routing basics. I understand that REAPER can be somewhat overwhelming because of all the options it offers. However, if you take them one at a time, you’ll discover their uses in no time. Happy music-making!