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Wednesday, 27 January 2016

Sidechain Compression And Gating

G’day ladies and gentlemen. Today I wanted to go over sidechain compression and gating and ways that it can be used to get some pretty cool sounds. Everything I’m writing about is covered in the video above, I just wanted to go over in a bit more detail here.

What Is The Sidechain?

Sidechain refers to the sound that is triggering the effect in your compressor or gate. When a sound source goes into the compressor it gets split. One part of the sound goes through the process of being compressed or expanded and then comes out the other side, and that’s what you hear.

The other part gets sent to the part of the compressor that senses what is happening in the sound to trigger the effect. It’s this part that hits the threshold of the compressor and causes it to reduce the volume of the sound coming out the other end. 

When you change the sidechain, you are affecting the sound that is being analysed by the compressor or gate. This means when you add EQ changes to the sidechain, you aren’t changing the EQ of the sound that you hear, you’re changing the EQ of the sound that the compressor hears.

In the example that I used in the video, I had a drum beat that was being quite heavily compressed (this was so you could clearly hear the changes I was making). I then pushed up the high pass filter on the sidechain and this meant that the lower frequencies that I was cutting out were no longer affecting the compressor.

This meant that the bass in the kick drum was no longer affecting the compressor in the drum beat. As we went higher, the snare triggered the compressor less and less and you could keep going up until only the very highest frequencies were causing the compressor to react. Of course you could do the same thing with the low pass filter.

This kind of thing can be very helpful, especially when you want to hone in on a specific frequency that you want to compress. Maybe your bass track has one note that sticks out too much, you can drop the filters in to focus on that note and only compress it.

Key Input

The key input is where things start to get a bit more fun. Now, instead of just changing the sound that’s triggering the compressor, you can put a whole new sound in. This means you can use any sound source to trigger the compression or gating on any track.

This is a very common effect used on lots of EDM style tracks. Usually the kick sound is used to trigger the compressor on the synth tracks. This makes the whole track sound like it’s pumping to the beat.

In the video, I use the sound of the kick to trigger the compressor on the bass. The sound I used was a very extreme example, but that’s just so you get the idea of what’s happening. In practice I would use a much faster release, a lower ration and a higher threshold. 

Used in a subtle way, this means that the bass track will drop slightly every time the kick is hit and then bounce back before you notice it. This means that you can have your bass nice and loud, but it won’t get in the way of the kick drum sound.

I use this same concept with guitars and lead vocals. If you put the compressor on the guitar bus that’s being triggered by the main vocals, it means that your guitars can be nice and loud but won’t drown out the singer. If you do it right, you won’t notice the guitars dropping in volume, but the vocals will seem to punch through the mix just right.


On the other side of things, you can use the gate/expander in the exact same way. Let’s say you have a bass guitar that follows the kick drum but they’re playing is inconsistent. You can put an expander on the bass that’s being triggered by the kick drum.

This will mean that the bass will punch up when the kick is hit and drop off a bit when it’s not. This trick will only work for some songs, but if it’s the right one you can get some pretty cool sounds out of it that will make it sound like your drummer and bass player are completely in sync.

You can use this same effect for heaps of other sound sources with varying degrees of success, but it’s worth experimenting with as you can really sculpt the feel of a track using this kind of dynamic manipulation.

Getting Creative

When I was at uni, I was trying to create a drum beat for a track I was creating. I didn’t have access to any of the sample plugins that I have now and was trying to rack my brain of ways to get a good sound.

From memory I managed to create a kick sound from hitting a big piece of wood with a hammer. I got the snare from flicking a piece of paper. I then used EQ and editing to get the sounds the way I wanted them. My main problem was getting a hi-hat sound.

I remember my teacher at uni saying that he liked to make his hi-hats sound like an aerosol can. So I thought, “why don’t I try to make an aerosol can sound like a hi-hat. So I recorded the sound of the aerosol can and then got the rhythm I wanted using a coin against a table.

I then put a gate on the spray can track and then ran the tapping track through the key sidechain on the gate. It took a little bit of messing about with the EQ on the can and the parameters on the compressor, but after a while I had a convincing hi-hat track.

This was great because it even had a bit more realness than the machine gun sound of a single hi-hat sample being played over and over. Plus, the sound of the hi hat was easily manipulated. I could even push the tapping track up if I wanted to get a bit of “stick” sound in there.

I have done this again since, using generated white noise and various other sources, but the point is that you can get very creative with the kind of thing. Creating semi-organic sounds unlike those that you can get from a synth or regular instrument.

Let me know if you have any comments, questions or sound ideas in the comments section below.

Until next time, have a good one!

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