Reference Manual
CHAPTER 20. LIVE AUDIO EFFECT REFERENCE 274
With Dry/Wet at 100%, the compressor is triggered entirely by the sidechain source. At
0%, the sidechain is effectively bypassed. Note that increasing the gain does not increase
the volume of the source signal in the mix. The sidechain audio is only a trigger for the
compressor and is never actually heard.
Note that FB mode and automatic Makeup are not available when using external sidechain.
On the right of the external section are the controls for the sidechain EQ. Enabling this
section causes the compressor to be triggered by a specic band of frequencies, instead of
a complete signal. These can either be frequencies in the compressed signal or, by using
the EQ in conjunction with an external sidechain, frequencies in another track's audio.
The headphones button between the external and EQ sections allows you to listen to only
the sidechain input, bypassing the compressor's output. Since the sidechain audio isn't
fed to the output, and is only a trigger for the compressor, this temporary listening option
can make it much easier to set sidechain parameters and hear what's actually making the
compressor work.
20.5.2 Compression Tips
This section presents some tips for using Compressor effectively, particularly with the
sidechain options.
Mixing a Voiceover
Sidechaining is commonly used for so-called ducking effects. For example, imagine that
you have one track containing a voiceover and another track containing background music.
Since you want the voiceover to always be the loudest source in the mix, the background
music must get out of the way every time the narrator is speaking. To do this automatically,
insert a Compressor on the music track, but select the narration track's output as the external
sidechain source.