Sidechaining is an indispensable, though sometimes overlooked, mixing and production technique, with an assortment of both utilitarian and creative applications. A fundamental tool in every engineer’s kit, you’ve certainly heard it in action. Here are a few possible occasions:

• When the kick drops in an EDM track, creating an audible pumping effect across the entire mix (think “Call on Me” by Eric Prydz or Daft Punk’s “One More Time”)
• When music gives way to a soloing instrument or soaring vocal melody
• When a song on the radio quiets in response to the DJ’s voice … and many more

Most effects with a sidechain, or key input, impact the dynamic range of a signal, and subsequently include standard and multi-band compressors, noise gates and expanders. Whenever you engage the sidechain, you’re telling the effect to monitor a different input source from the actual track being processed.

The bulleted examples above refer to the most common method, which is sidechain compression. Whether used heavy handedly to pump a techno beat, or gently to organically balance mix elements against one another, the primary effect of sidechain compression is “ducking”—applying gain reduction to a source, or, in some cases, an entire group or mix, in response to another sound.

We’ll equip you with a few essential tips for sidechaining in your own productions, as well as cover the basics. Our aim is to inspire you to discover new and novel ways of deploying this technique to tighten up your mixes and give them a dynamic, punchy edge.

Table of Contents

How Did Sidechaining Originate?
How to Use Sidechain Compression in Your DAW
What Should I Be Sidechaining for Cleaner Mixes?
   The Kick to the Bass
   A Solo Instrument to the Mix
   Lead Vocals to a Reverb Return
The Best Plug-ins for Sidechain Compression
   FabFilter Pro-C 2
   Arturia Comp FET-76
   Universal Audio API 2500 Bus Compressor
Sidechaining Demystified

How Did Sidechaining Originate?

Like so many audio practices we consider standard today, sidechaining was born of a resourceful mind seeking to solve everyday problems. Let’s set the scene: the pioneer is sound designer and recording director Douglas Graham Shearer, and the period is the 1930s. Shearer, very pragmatically, needed a way to tame sibilance in dialog recordings—a pursuit that would lead him to conceptualizing the modern de-esser as we know it, and inventing sidechain compression in a single swoop.

He split the primary dialog signal and fed it to both a compressor and an equalizer, using the latter to essentially create a band pass focusing on the most sibilant frequencies. By feeding the EQ’s output back to the compressor, Shearer developed a way to process the main dialog track, only when the harshest “s” sounds occurred. A stroke of genius, Douglas Shearer was able to set highly specific parameters under which his compressor should operate.

In subsequent decades, the most pervasive use of sidechain compression was initially in radio, allowing DJs to talk over the intro or outro of a tune. But it certainly didn’t stop there.

First, it’s worth noting a famous instance of what sounds like sidechain ducking but is actually an example of over-compression. Legendary Beatles engineer Geoff Emerick stylistically crushed Ringo Starr’s drums on the psychedelic 1966 jam “Tomorrow Never Knows,” resulting in a constant deluge of fizzy cymbals, momentarily ducked by powerful kick and snare hits. Emerick’s compressor of choice, in this case, was the tube-based Fairchild 660, which he became an artistic master of.

Pictured: Universal Audio Fairchild Tube Limiter Collection Software Plug-in

Sidechaining with analog hardware became more prevalent throughout the ’70s and into the ’80s. In 1979, Producer Steve Lillywhite and engineer Hugh Padgham happened upon a whip-like snare drum effect while working on Peter Gabriel’s third solo record.

The gated reverb technique—in all its quintessentially ’80s glory—became a staple sound of the era. It was originally achieved by feeding a close-miked snare to a reverb unit, outputting the reverb to a noise gate and keying the snare mic to the gate’s sidechain input. Hear it on “Intruder” by Peter Gabriel; “In the Air Tonight” by Phil Collins; and numerous hits by Prince, to name a few.

Into the ’90s and beyond, hip-hop legend J Dilla injected an influential, kick-heavy pumping sound to his beats that would transcend the decade and genre, activating scores of aspiring producers and beatmakers in the early ’00s. That rhythmic, bumping pulse is the signature sound of slamming sidechain compression, and dance music would go wild with it in the new millennium.

Looking back, analog sidechaining was a tad tedious in those early years, requiring hardware with dedicated sidechain I/O and a bit of patching knowhow. With the digital revolution, it became an increasingly popular way to cleverly add interest to productions. Today, it’s a go-to software technique for any well-rounded engineer.

How to Use Sidechain Compression in Your DAW

Sidechain capability is a standardized feature of most dynamics plug-ins. Even many emulations of hardware, which didn’t originally have a sidechain, gain one in software form. In that sense, you’re much freer to experiment with the effect in the digital domain. The step-by-step process varies slightly from plug-in to plug-in and DAW to DAW, but the principles of digital sidechain compression are no different than those of analog.  

You’ll want to start by inserting a compressor directly on the track you want to process—i.e., the sound receiving the gain reduction. Most stock compressor plug-ins, including those found in Avid Pro Tools, Ableton Live and Apple Logic Pro X, among others, have a built-in sidechain. The next step is to choose the key input, or trigger signal, from the selection of tracks in your session.

In Ableton Live, for example, it’s as easy as loading an instance of Compressor, enabling the Sidechain button and choosing the Audio From source in a dropdown list. In Pro Tools, on the other hand, you’d first have to create an auxiliary bus, route your key track to it and set the compressor’s sidechain input to that bus.   

From here, it’s all about adjusting compression parameters to taste. Whether that’s for a modest amount of ducking or a beefy pumping effect is up to you.

What Should I Be Sidechaining for Cleaner Mixes?

Now that we have the fundamentals of sidechaining down, we can cover a few ways of incorporating the effect into your mixes. As is the case with everything audio, there are no hard, fast rules—only common practices, concepts and starting points to help you sonically embark on your own bon voyage.

The Kick to the Bass

The most pervasive illustration of sidechain compression is when it’s used to keep a kick drum and bass out of each other’s space. Low end can be a tricky area to mix in virtually every genre, and managing a hard-hitting kick and booming bass guitar or synth is no small feat.

Leveling and EQ are great places to start, but if you still can’t find the cohesion between your most important low-end elements, sidechain compression can be a skilled mediator. Drop your favorite compressor on your bass track(s), and key its input to the kick. Each time the kick plays, the bass will duck to give it more room to breathe.

This technique offers better separation between the two, which can reduce muddiness and increase the articulation, punch and power of your lows. The following settings are a good place to start:

• Set a moderately fast attack around 10 ms, so that the compressor reacts quickly enough to pull the bass underneath the kick’s initial transient
• Set a medium-fast release time of around 50 ms—it should be long enough to sound smooth, without introducing artifacts or pumping (unless you’re going for that, of course)
• Try a fairly standard ratio of 4:1 to get going, but don’t be afraid of higher ratios for more pronounced compression
• Adjust the threshold for 3–6dB of gain reduction

A Solo Instrument to the Mix

Building on the idea presented above, sidechain compression works for broader mix moves as well. While volume automation is a logical step when tasked with carving room for a guitar solo in a dense arrangement, sidechaining is a soulful move. It typically does the job a bit more gracefully when you’re attentive to settings, and with greater dynamic interest. Plus, depending on the plug-in or hardware emulation you use, it can introduce desirable sonic coloration to your mix that volume automation does not.

Put the guitar solo on its own track, and simply key it to the sidechain input of a compressor on your mix bus. Better yet, compress instrument groups separately, so you have individual control over the amount of gain reduction applied to each. When the solo kicks in, the band steps back. When the solo’s over, it steps forward again.

Sidechain compression can give the guitarist (or any soloist) the shine they deserve, while retaining the natural mix balance you’ve worked hard to achieve. This technique is also how some electronic producers create their pumping effect, usually sidechaining the kick to the mix and syncing the compressor’s release time to the song’s tempo.

Lead Vocals to a Reverb Return

Reverb is one of the most vibey effects at our disposal. Untrained ears won’t always pick up on the incremental dB shift of gentle gain reduction, but everyone can identify the sound of echo.

Reverb is also one of the harder effects to manage; haphazardly applied, it can turn into a washy mess, pushing prominent instruments into the background. One way to keep reverberation in check—especially on a crisp, contemporary pop, R&B or hip-hop vocal—is by using sidechain compression.

If you love the long trails on your lead vocal but are having a tough time preventing them from swallowing the singer entirely, insert a compressor on the reverb return. Enable sidechaining and set its input to the vocal track. Between phrases, the compressor will let go, and reverb will swell up to fill the gaps. Then, it’ll neatly duck away as the vocalist begins another line.

The compressor’s release time is key here, so you’ll want to see how various settings react in your mix’s context and use this parameter judiciously. With a release that’s too short, the reverb will rise back up to full volume in a potentially distracting way. If it’s too long, gain reduction could remain almost constant, mitigating the benefit of sidechaining in the first place. Once you’ve established that balance, though, the effect can be a real game changer.  

As a slight aside and tie-in to the EDM pumping anecdote above, you can also sync your reverb to the track’s tempo for ultraprecise, clean trails. Simply divide 60,000 by the BPM to receive a quarter-note value in milliseconds. Halve that number for an eighth note, double it for a half note, and so on.

More Quick Tips:

• Duck snare from overheads by sending its close mic to an OH compressor
• Duck rhythm guitar from vocals and target specific midrange frequencies with a multi-band compressor
• Beef up your kick drum with a pitched sine wave by inserting a noise gate on the tone generator and sidechaining it to the kick

The Best Plug-ins for Sidechain Compression

From colorful to transparent and everything in between, there’s no one-size-fits-all approach to choosing a compressor plug-in with built-in sidechaining. We’ll recommend a handful of standouts, but there are hundreds of viable choices, including many based on classic analog gear, and others conceived completely in the digital realm. To say it succinctly: you have options.

Really, there’s no better place to start than with the stock dynamics processors in your DAW. Those tools are already at your disposal, so you can start experimenting with sidechain functionality right away. And when you’re ready to zhuzh up your plug-in library, the following selections are excellent intros to the vast world of software compression.

FabFilter Pro-C 2

Part of the brilliance behind FabFilter plug-ins is that they’re simultaneously easy to use and intriguingly complex. Featuring eight different compression styles—including application-specific settings for vocals, buses, pumping and more—the FabFilter Pro-C 2 compressor is widely considered a “10/10” by everyday hobbyists and industry pros alike.

Pictured: FabFilter Pro-C 2 in Logic Pro X—the track's kick drum is sidechained to the bass for smooth, easy ducking

Sidechain triggering is, of course, a regular inclusion, and the Pro-C 2 also comes with a dedicated filter section for external sources, which lets you further refine how the compressor responds to a signal. The UI is fabulous, it’s as simple or complicated as you want it to be, and the sonics are as good as they get. FabFilter’s Pro-C 2 is desert-island software.

Feel free to check out the rest of the collection.   

Arturia Comp FET-76

Having an 1176 in your arsenal is non-negotiable—alright, maybe there’re some rules. Arturia’s Comp FET-76 faithfully models one of the most celebrated and widely used outboard processors of all time and laces it up with advanced sidechain processing, wet/dry for quick parallel, pre-delay, onboard EQ and more.

Lauded for their component-level recreations of timeless analog treasures, the Arturia Comp FET-76 brings racks on racks of iconic peak limiting to your DAW.

Pictured: Arturia Comp FET-76 Software Plug-in

Sonically, the 1176 is aggressive and gritty thanks to its solid-state circuitry—the in-your-face sound is often summarized simply as being “hot.” In other words, the 1176 tends to be precise, punchy and present, grabbing instruments and interacting with them rather than acting on them. Not for those faint of analog coloration, the infamous “All Buttons In” mode, in which every ratio is engaged, downright distorts signals. Apply liberally.

In the meantime, check out our Guide to the Universal Audio 1176 to discover more about why this hardware is so special, as well as how you can coax the most from it for your mixes.

Universal Audio API 2500 Bus Compressor

Automated Processes Incorporated is right up there with Universal Audio as far as legacy goes in the recording space—together, industry-renowned magic is made. UAD’s native and DSP plug-ins are among the top analog-emulated models available, and the API 2500 bus compressor is surely no exception.

API’s patented THRUST circuitry works wonders for punchy bottom end, automatically qualifying it for drum/bass subgroup sidechaining and aggressive EDM pumping. Used as a regular bus comp, the 2500 has a remarkable way of preserving transients and dynamic integrity, while glueing mixes together in a desirable way.

Pictured: Universal Audio API 2500 Bus Compressor Software Plug-in

Speaking of glue, SSL’s Bus Compressor 2 is another mythical beast digitally reimagined with modern functionality—including sidechain. Also, when you’re ready to go hands-on with a major addition to your hardware, the API 2500+ stereo bus compressor is available.

Sidechaining Demystified

Sidechain compression is a surefire way to straighten out wonky levels in a smooth, refined manner. Regardless of where you are in your recording and mixing journey, sidechaining doesn’t have to be an unapproachable or overly complicated concept. In fact, it’s quite simple, and we hope you’re encouraged to employ it throughout your projects as you deem fit.