What is Sidechain? 3 Important Sidechaining Techniques

A vu meter showing compression from a sidechain trigger

What is sidechaining?

Sidechaining is the act of sending a signal from one channel to another to be used as an input trigger. However, unlike a normal send, a sidechain does not transfer sound. Often considered a more advanced technique, it has a multitude of uses but is misunderstood by many. There are plenty of great ways that you can utilise sidechaining in your day to day audio work in order improve workflow, ease mixing, and create powerful effects.

Sidechain Compression

The most known and often used of sidechaining techniques, sidechain compression appears heavily within the urban and electronic music scenes. Have you ever noticed that huge pumping sound on the kick of a dance track? That’s sidechain compression. The basis for this technique is to use the signal of one sound as a trigger to compress (essentially duck) another sound. This is common in dance music where we use the kick drum to duck the bass line and synth sounds. This offers a huge, rhythmic pumping sound and helps to drive the track.

However, this is not the only use for sidechain compression. A slightly more advanced approach to this technique would be to subtly create space in a mix. An example of this would be the use of a multi-band compressor to suppress a specific frequency range at key moments. Your track may have a driving guitar line throughout with the introduction of a brass section in the chorus. These two sources are likely to operate quite heavily in the 4kHz region. In order to keep that driving guitar sound but let the brass shine through, sidechained multi-band compression can shave 1-2dB off the guitar by using the brass as the source signal. This way, you can let both instruments be dominant within the mix without creating a messy mix.

Sidechain Equalisation

Frequency masking is often a huge problem in amateur mixes. The build and subsequent clash in harsh frequency ranges can make a great song sound awful. Piercing highs, muddy lows and bloated mids are something we never want to hear. This is where sidechained equalisation can help.

A sidechain EQ showing frequencies being ducked to fix frequency masking.These days, most parametric EQs will offer a sidechain input. If yours doesn’t, I recommend checking out Fabfilter and their line of EQs. By sidechaining one signal into the EQ of another, we can visually see the areas where two sounds clash. We can then go about removing unnecessary frequencies and tackling over populated areas.

A great example of this would be the contention between a lead guitar and a vocal. Both working in very similar frequency ranges, the two can often bury each other. By utilising sidechain equalisation to tackle this frequency masking, we can duck some of the important vocal frequencies from the guitar line. This ensures clarity and power.

Sidechain Reverb/Delay

This technique is predominantly stylistic but can offer some brilliant and unusual effects. By sidechaining a signal into its own effect send and using a compressor, we can not only improve clarity but create huge effects swells in the transitional sections of our music.

Let’s say you’ve got a lead vocal which you have fed into a delay send in order to add some colour and texture to your track. However, sometimes these delays can get a little cluttered and the words become hard to hear. You like the amount of effect you’ve used and you just can’t seem to balance the two. By sidechaining the vocal signal to its own delay send and keying it into a compressor at the end of the effects chain, you can use the vocal to suppress its own effect send, thus ducking the delays when the vocal is playing. This will improve clarity in the mix as well as allowing the delays to fill up space within the song.

Equally, by setting the compressor to very high ducking (10-20dB), you can create wonderful explosive swells from delay and reverb at the end of vocal lines. This is a very abstract technique but certainly, one that could set you apart from the crowd.

TL;DR

Sidechain is a wonderful tool. Contrary to popular belief, it isn’t just used for dance floor pumping and if learned properly, can bring incredible ease to the mixing process. Play around, try different variations, and create something new.

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