What is Side Chain Compression
Side Chain Compression enables you to have the compressor react from a separate signal then the one that is being compressed. In essence one signal will be ducking under the other. There are a few different uses of side chain compression. One of the classic uses is when A radio DJ and some Club DJ’s talks over a song that is playing. Wen the DJ talks there is a ducking effect on the music. This effect is automatic so the DJ does not have touch the volume fader when talking. Another classic use is the pumping effect that is common in a lot of EDM music. Every time the kick drum hits the side chain compressor reacts and creates A pumping effect on the other elements of the song. Most commonly the Bass but EDM producers usually pump the synths and pads to. There is also a way to use the side chain compressor so that sculpts the destination audio just a little but so that the source audio can stand out in a subtle way. A great example if this to keep the kick drum and bass form competing for the same space. you can side chain the bass to the kick drum, set a fast attack, fast release, and a lower ratio then you would for the pump effect. In the mix you wont notice the bass ducking but you will notice the kick having a little more punch. I tend to side chain each individual element of my mix to my kick drum, including my sends. I do this with fineness so that you do not hear any pumping in the mix you just hear a phat punchy kick drum. This technique can be used with any thing that you want to slightly stand above your mix. Some other examples are vocals as the source to compress a guitar or synth, in Jazz music you can set the side chain compressor on the lead instruments so it will stand above the others, when you want a lead guitar or synth to have more presence during the solo without having to turn it up, and much much more.
When producing a song you can easily end up with a lot of musical elements. If your not careful these elements will start to compete to be heard. Like how a guitarist is always turning up their amp, then the drummer plays loader, the bass player turns up, and then eventually the vocalist can’t sing anymore because the singer voice got trashed from trying to scream over everyone at practice or at a gig. This is called Volume Wars, and this can happen in your mix. Volume wars is when you want to hear the bass more so you turn it up, now you need to turn the kick, turn up the vocals, turn the synths, oops now the bass is to low… turn it up. The master buss is way in the red so you decide to compress it, limit, crush it.Then you mix it down play it in your car and it sounds like dodo. Just like most wars their is not winner. A much better method exists and that is called Subtractive Mixing.
Subtractive Mixing is the opposite of volume wars. In Subtractive mixing if you want the kick drum to stand out, you listen to your mix, figure out what is competing with the kick drum and turn it down, pan it, or use a Side Chain Compressor. The glorious Side Chain Compressor is one of Subtractive Mixing’s greatest heroes! As mentioned previously you can use the Kick drum to cause the bass to duck under when ever the kick drum plays. If you set the settings with a fast attack and release, as well as a smaller ratio, you will not notice the ducking effect in the mix, but the kick will punch.
How to set up A Side Chain Compressor in Ableton Live
In you Ableton Live Browser select Audio Effects locate the Compressor and drag a default compressor into your Bass track. You can get a Default Compressor what seems to be the entire Compressor folder. This is how you can get a default patch with all Ableton Live devices.
Locate the black downward triangle inside the yellow circle on the top left side of the compressor. Clicking the Triangle will open up the hidden side chain and eq features of Ableton Live’s compressor.
Click the rectangular box that says Side Chain to enable the side chain compressor.
Under the words Audio From you will see a drop down menu with “No Input” selected. Click the drop down menu and select your kick drum, drum track, or what ever you want the side chain compressor to react from.
The second drop down menu will now be available. You can use this menu to select the the point at which the source audio is pulled from.
Pre Effects – The source will be pulled before any effect processing happens, The source will remain raw an un altered. this is advantages if your early on in the mixing because anything you do to the source will not effect your how the side chain compression reacts.
Post Effects – The source will be pulled at the end if the signal chain but before the track fader and track activator (mute) button. The main advantage here is even if you mute the track the side chain compression will still react to the source.
Post Mixer – The side chain compression will react to the signal that comes after the track Fader, track Activator (Mute), and Panning. The advantage of this setting is if you mute the track the side chain compressor will stop reacting from the source.
Also there may other options based on what devices you have in the source track, Drum Racks, Instrument Racks, and Effects Racks will all have different spots that you can tap the signal from. One example in a drum rack you could pull the signal from the kick drum or kick drum group enabling you to leave the drum rack alone and tap just the signal from the kick.
Ableton Live’s Compressor has Two Dry/Wet Knobs. the one that is in the Side Chain section on the bottom left is to mix between the compressor reacting from the side chain signal as the source and the original signal as the source. The Dry/Wet knob on the main part of the compressor located bottom right is to mix between compressed signal and dry signal.
Next to the Side chain Activation button you will see the EQ section of Ableton Live’s side chain compressor. when you have side chain enabled this EQ will shape the source audio (the audio you are tapping into) of the side chain compressor. One handy use for this is if you want to be able to mute the drum rack or drum buss and have the side chain compression stop reacting. you can set the Audio From to post mixer of your drums. Turn on the EQ. set the Filter type to Low Pass. Adjust the Frequency of the filter to some where between 50 and 70 Hz. adjust the Q to bust the volume at the cut off frequency. Now the side chain compressor will react to the kick because you pretty much filtered out everything but the sub kick. this trick will allow you to mute the drum buss and stop the side chain compression. This technique can be very handy for live performance with Ableton Live.
One thing to note. If the side chain is off and the EQ is on, the compressor will react just like a normal compressor. So the source audio will now be the audio that is from the same track that the compressor is on but the source audio will be filtered and the compressor will react to the filtered audio You will not hear the results of EQ but you will hear the compressor only reacting from the EQ’d audio. Theoretically you could use Ableton’s Side Chain Compressor like a Desser using this trick.
You may have noticed by now that there is a little headphone icon in between the Side Chain button and the EQ. This headphone Icon will allow you to hear the source that is being tapped. This is handy if your attempting to use the above mentioned EQ tricks to shape the way the compressor reacts. Enabling the headphone will allow you to hear the results of the EQ effects on the source audio which will give you a better idea of how the compressor will react.
Basic Compressor Control Over View
Now that we have the source audio routed and potentially the EQ set, we can start to adjust the compressor parameters to get the desired results. The four primary parameters of any compressor are Threshold, Ratio, Attack, and Release.
Threshold is the amplitude that a compressor reacts, when the source audio is below threshold the compressor does nothing but when the source audio is above threshold the compressor will react based upon how the Ratio, Attack, and Release are set.
Ratio is how compression is applied when the compressor reacts. as an example a compressor with a 2 to 1 ratio means, for every 2db the source audio goes above Threshold the compressor will only allow for a 1db increase in volume. So if the source is 4db above threshold with a 2:1 ratio the compressor will only allow the audio to output 2db above threshold.
Attack is how fast the compressor will react when the source goes above threshold. Setting the Attack really fast will result in the compressor responding as soon as threshold has been breached where as in the case of a slow attack the compressor will ramp up based on the time value set by the attack. Ableton’s compressor can be set between .01ms and 1 second. If the compressor is set with a 1 second attack it would take 1 second for the compressor to reach the full amount of compression. For side chain compression settings it very common to use a fast attack. A fast attack can sometimes result in a clicking noise with ableton live 9’s new compressor but live 8’s compressor with the model type set FF1 can react very fast and clean resulting in no clicks. You can use the old compressor in live 9. The ableton live 8 compressor will have a similar interface as the live 9 compressor with the added upgrade button but it will use the algorithms and features of ableton live 8’s compressor. FF1 mode is best for chaining. If you don’t have Ableton Live 8’s compressor you can download it here.
Release is how long the the compressor stops reacting after threshold has been breached. Ableton’s compressor release values can be set between 1ms and 3 seconds. A fast release is good if you are attempting to just bring out the kick but create no noticeable effect on the audio you are compressing. A slow release is good if you are trying to create a Pumping effect where the compressed audio seems to swell up every time the source audio of the kick drum is played. The pump effect is common in allot of EDM. If you have Auto Release set then Ableton Live’s compressor will adjust the release time automatically
The Output Gain gets an honorable mention. you can use the output gain to increase or decrease the output volume of the compressor. The traditional way to set a compressor is to adjust the output volume so that no increase or decrease of volume to the compressed audio happens. The compressor is traditionally used to adjust the dynamic range of the signal not the amplitude. If Make Up Gain is on the compressor will basically try to do this automatically but you still may need to make adjustments to the output gain.
How To Use A Side Chain Compressor
There are many reasons and uses for side chain compressor. I’m going to cover two most common uses and I like to call the two primary uses The Tool and The Effect. The tool is when you want to do things like bring out the kick, get the vocals to ride on top, or punch the guitar solo through the mix. The Effect is the pumping sound that you hear in a lot of electronic dance music. The effect’s results are noticeable and used as party of the song. Where as the tool style of side chain compression will not necessarily be noticed directly but the listener will hear the effects of a clean tight mix. The tool helps creates space for elements of the song to sit in.
The Tool creates space. If you want a banging kick, the vocals to ride, in your face leads, setting your side chain compressor in this style is the magic. The tool is very subtle and fast, you should not directly hear the side chain effects compressing but you should hear the source stand out. I prefer to use Live 8’s compressor in FF1 mode because the FF1 mode responds very well to fast attacks and fast releases. Live 9’s compressor and live 8’s compressor when not in FF1 mode will make audible clicks when set to faster attack and release settings. If you don’t have live 8’s compressor here is a link.
Also setting a smaller ratio and keeping the threshold at a higher amplitude is usually better. You want the effected audio to just duck under the source audio, but when the source is not playing you want the effected audio to sound full. For a banging kick drum I will put a side chain compressor on the bass set to FF1 with a very fast attack.. usually around .02 ms and a very fast release generally between 10 and 40ms. Just enough for the initial transient of the kick to punch through. I then set the ratio and threshold to just nip it down a bit when the kick drum plays. Make sure you don’t really notice the bass ducking but you do notice the kick having a bit more presence. I then copy and past that compressor on every single including returns with the exception of the kick and master buss of course. On each track i make mild adjustments so as to not be noticed on the track. Also make sure the side chain compressor is the last compressor in your chain, in fact the only thing I personally put after my side chain compressor is other side chain compressors if needed and a Limiter. The reason I side chain everything to the Kick is because if you gently compress everything to the kick you make a much cleaner and bigger pocket for the kick to ride rather then bussing everything but the kick to its own track and compressing it with 1 compressor. Try it on your mix and you will notice a massive difference.
You can apply a similar principle to other elements of your track that you want to bring out. You don’t necessarily need to compress everything to your vocals but defiantly hit the competing elements. A nice trick for vocals is to use a fast mild side chain compression on the reverb return track in order to let the initial transients of the main vocal ride over the reverb vocal allow for the vocals to stay in front of the mix. Reverb is a spacial effect and you can accidentally push the vocals back if you use to much reverb.
The Pump Yes!! Raise that fist in the rhythm of the kick with a banging four on the floor! mind melting bass drum and swelling synths to get the dance floor moving. Is it over used? well yes. Is it awesome? o yes! Can you use this in other forms of music to create really cool effects? of course. Try using vocals as the source and have a pad pump of the vocals.. try hats.. try everything! So i guess your wondering how exactly you do the pump. It is simple.. just set up you side chain compressor and give it a slower release. you can also adjust the attack for some interesting results. For the mind bending pump like in Trance and progressive house use a big ratio and bring down the threshold really low. You want to hear the effect.. you want people to notice. you can set the compressor to have a big massive pump and then use the dry/wet knob on the bottom right of the compressor to bring in and out the pump. So after the first drop maybe the Dry/wet set about half way but then on the second drop bring the wet all the way up to create more energy and excitement. This is also a good way to get that Bawoom Bawoom like in Goa Trance by pumping the Bass synths from the kick.
Thank you for reading and I hope this was helped you understand what a side chain compressor is and how to use side chain compression in your mixes. My name is Jimmy Allison and I am an Ableton Live Certified Trainer. I teach Ableton online and locally in Austin, Texas. Feel free to contact me for more information about Ableton lessons.