Creative Ducking & SidechainingJune 25, 2013
You’ve heard music duck under the DJ’s voice, the basses that pump in response to the kick drum, and you might be looking for a way to add echoes to a track without cluttering up the mix. It’s easy to achieve these three effects with the same basic technique: Sidechain Compression. Sidechaining is what happens when one track reduces in volume in response to another. For example, the audio below features music ducking under a voice like it would with a radio DJ. This will be the second technique we look at, and it builds on the first technique, duck delay.
Duck Delay Step 1 - Setup
To begin, I’ll route a pluck sound’s mixer track to another track which will
hold the effect. So I have two tracks, a dry track, and an effected track, both
routed to the master. On the effected track I’ll load a delay or reverb and set
it to 100% wet, 0% dry. Setting up an effect this way is essential for the
ducking technique, but there are other advantages to this setup as well.
Benefits of Send Effects:
- I have two separate mixer sliders and pan knobs, one dry and one wet, for easy mixing.
- I can send audio from other mixer tracks to this plugin as well, saving CPU.
- I can use separate compression, EQ, and stereo width on the effected signal.
In this example, I panned the dry and wet signals left and right, and I EQ’d the wet signal to be tinny. The first bar is dry for comparison.
Duck Delay Step 2 - Sidechain Compression
The delay is a bit overpowering and makes the track too busy. So I'll have the delay duck under the dry audio, playing only between the dry hits. I’ll put a compressor on the wet effects track and turn
the threshold all the way down, and I’ll set the ratio to three-and-a-half. The
compressor should have an envelope that snaps down whenever audio comes in and
relaxes when no audio is playing. The result will be that we can no longer hear
the effected track.
Next, the basic idea is to find the place to select which input the compressor will respond to. It varies for each DAW, but the image above shows the location in FL Studio. In the image above, the audio is being compressed by itself (the standard behavior for compressors). However, in the image below, the "DRY" track has been selected, which means that the compressor reduces the Wet signal in reaction to the Dry signal playing.
The result is that the delay only plays when the dry pluck is not playing. Because of the panning it makes for a cool ping pong effect and a groovy sequence, and I can make the delay track rather loud without overwhelming the mix.
Radio DJ Voice Auto DuckThe above technique can be tweaked to achieve all sorts of popular effects. For, example, if you turn up the threshold to a medium setting, the compressor won’t totally mute the audio, it will just turn it down a bit. If you turn the send audio knob all the way down, you can still use that audio’s envelope for the sidechain compression without any bleed into the mixer track. I highlighted the knobs and settings in the screenshot below. With these two tweaks, you can do that Radio DJ thing where the volume of the music automatically ducks down as the DJ speaks.
- Duck a bass synth under the kick drum for that sucking synth effect
- Duck pad sounds under the drums to gain headroom
- Duck a big reverb under vocals to add a big flourish at the end of each phrase
- Duck a delay under other instruments, like a lead or piano
- Duck a choir of ducks under another duck while ducking all the ducks under a woodchuck
- What other creative uses are there for sidechaining? Let us know in the comments