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What Is Compression?
Compression is the process of keeping an audio signal within a certain dynamic range (a.k.a, a certain volume range). To use a compressor, you pick a volume level that you always want your instrument to sound within—never softer and never louder. Then you set a compression level, which determines how sensitive the effect will be. At this point, once the compressor is engaged, every note that’s played too quietly will be boosted to fit into your set volume range, and every note that is played too loudly will be softened to fit the range. Your instrument will always be heard in the dynamic range you’ve specified.
Advanced compressors also allow the user to dial in the “attack time” (how quickly the effect engages) and “release time” (how quickly it shuts off). They may also have tone controls to hone in on particular frequencies. A multiband compressor can isolate multiple frequencies and compress them, while leaving other frequencies alone.
What Is Sidechain Compression?
Sidechain compression is a bit different. It is a type of compression where the effect level on one instrument is controlled by the volume level of another instrument. A common example would be making the compression level on a bass controlled by the output volume of the kick drum. So when the kick drum sounds, the bass gets more compressed so it can keep cutting through the mix.
Sidechain compression is particularly popular in dance pop because it allows instruments to cut through a mix at all times. When other instruments in a mix get louder, the sidechain effect increases so that the track it’s on will never be drowned out.
How Do You Use a Sidechain Compressor?
Most people use sidechain compressors via software plugins on their computers. If you’re producing a track using one of the popular digital audio workstations, it is likely that these programs have sidechain compressors already built in. However, a lot of professional musicians prefer third party plugins to handle this effect.
Popular DAWs include:
- Pro Tools
- Digital Performer
- Fruity Loops
What Is a Sidechain Compression Plugin?
Even though programs like Ableton or Logic have built in sidechain effects, professional producers will often turn to special “plugins” that have excellent presets—settings tuned at the factory by the product’s designers. Most sidechain plugins only do one thing—sidechain compression—whereas an expansive program like Logic or Pro Tools does so many things.
So rather than waste a lot of studio time tinkering to create sidechain parameters, producers rely on these presets to simply “plug and play.” Learn more about plug-ins with deadmau5 here.
What Genres of Music Use Sidechain Compression?
Sidechain compression can theoretically be used in any genre of music, but by far, it is most associated with dance music—EDM, house, and pretty much any other genre you’d hear in a contemporary nightclub.
These genres, with their propulsive 4/4 time signatures, rely on a steadily pumping bass sound to keep people dancing. That can mean bass guitar, kick drum, or bass synthesizer. The fact is that any instrument and any frequency can be boosted by sidechain compression, but the effect has become almost synonymous with bass frequencies in club music.
To hear an example of heavy sidechain compression, listen to “One More Time” by Daft Punk. At 00:45, a kick drum enters the mix. Listen to the effect it has on the bass: it’s almost a pulsing effect.
On the other end of the spectrum, you’re pretty much guaranteed to never hear sidechain compression in acoustic-based music. Orchestral classical music, which is highly reliant on subtle dynamic changes, would not be a good match for sidechain compression. Neither would folk music, although regular compression is commonly used to bring out the subtlety of a vocal line or fingerpicked guitar.
Other Uses, Tips, and Tricks for Sidechaining
Sidechaining doesn’t have to only be about bass. Consider these uses as well:
- Use sidechaining to bring out vocals. Remember, the effect is about letting a certain instrument cut through the mix. The earliest form of sidechaining was done by DJs who wanted their voice to cut through a complete instrumental mix. The same thing can be done to make sure your singer is heard over all the backing tracks.
- Use sidechaining to isolate certain frequencies. If you have access to a multiband compressor (most programs like Logic and Pro Tools and Ableton have them built in), don’t apply the sidechain effect to an entire track. Apply it only to certain frequencies within a track. Maybe you’re playing some funk guitar and want the upper-mids to cut through. Maybe you’re playing a gnarly synth and you want the upper frequencies to cut through. By only sidechaining certain frequencies and not the whole track, you can make these specific choices come to fruition.
- Use different sidechain presets or plugins on different tracks. Try running two different forms of sidechain compression on the same mix. The compression you put on the drums might be different than the compression you put on the bass. Experiment and see what effects you can generate when you mix and match.