Sidechaining usually describes the practice of controlling the compressor on one track with the output of another. “Ducking” was one of sidechain compression’s earliest uses: On live radio or TV, the announcer’s voice would trigger a compressor on the music to attenuate the volume while the person spoke. A long release on the compressor would keep the music low during short pauses of the dialog. These days in pop music or other genres where the vocal sits up front in the mix, engineers may use a subtler version of this ducking, setting the compressor with a lower ratio and shorter release and perhaps compressing only midrange tracks that conflict with the vocal, rather than compressing the entire mix.
Most modern DAWs have compressor effects with sidechaining built in, but you may also want to look into some plug-ins that specialize in sidechain-style effects for electronic music, like Nicky Romero Kickstart ($15), Cableguys VolumeShaper 4 ($40), or Xfer LFO Tool ($49), which simulates sidechain compression and performs other effects. Here are some other creative outlets for sidechaining, going from common to unusual.
Fig. 2. Live’s stock Compressor on a bass group track with the sidechain input set to the kick drum. The Ratio is noticeable but not extreme, and the Attack is slightly open to allow some bass transients. CLEAN UP BASS MUD
A common cross-genre use for sidechain compression attenuates the volume of your bass with the kick drum, so the two low-end elements don’t conflict too much in the mix. Drop a compressor on the bass track or track group. You may have to send the kick track to a bus and then set the compressor’s sidechain input to that bus. In other plug-ins, like Ableton Live’s stock Compressor, just set Sidechain Audio From to your kick track (Fig. 2). Make sure the compressor’s threshold is low enough for the kick to trigger it. You usually want a short attack and release on the compressor, so that the effect on the bass cleans up low-end mud, but is otherwise hardly noticeable. Lengthening the attack a bit allows more transients in the bass and may make it sound punchier.
THE PERFECT PUMP
Fig. 3. Xfer LFOT ool performs other effects like tremolo and auto- pan as well as sidechain-style compression, without the need for routing channels. This compression preset waveshape makes for some pretty serious pumping. Dance genres like filter disco and French house in the ’90s and early 2000s popularized extreme pumping of the entire music mix (besides the kick) from sidechain compression, and today some amount of pumping in dance music and R&B is almost mandatory (Fig. 3). This is similar to the previous example, except this time put the sidechained compressor on a group track containing everything but your kick or drum group. Increase the compressor’s ratio for more extreme pumping. A short compressor attack will make the effect sound sharper, while a slower attack will smooth it out. A too-short release may sound distorted, while a too-long release will erase the pump, so dial in something to taste in the middle.
SPLURGE ON EAR CANDY
You don’t always have to trigger the compressor with a kick. Just like you can use sidechaining to clear up bass mud, you can also use it to settle frequency disputes in the mid- or high-range. Say you have a track with persistent synth pads or long, sustained strings, but you also have some SFX ear candy, a lead arpeggio, some woodwind flutters, etc. going on in the same frequency range. Put a compressor on the sustained sound, and set the sidechain input as the other track that’s fighting for space in the mix.
Fig. 4. Live’s stock Gate on a looping bass patch, set to open on the sidechain input from the kick drum. UNLOCK THE GATES
Sidechaining is not just for compressors anymore. Many DAWs—such as Live 9—include noise gates with sidechain inputs for opening the gate, thus making the sidechain input add sound rather than scoop it away. One use for this would be to record a constant loop of a single low bass note—the root note of your song’s key—put a gate on it, and use the kick drum as the sidechain input to open the gate (Fig. 4), giving the kick another layer of oomph.