Effect Sidechain Routing

Sidechain section

The Compressor, Dynamics and Noisegate effects feature sidechain inputs that can be connected to various signals:

• Internal: the effect's input.
• Band Effect In: the Band Effect's input (available if the effect is in a Band Effect).
• Track: the output of another audio or softsynth track (available if the effect is in a Track).
• Effect Send bus: the mix of the Effect Sends of Tracks and Groups (available if the effect is in a Group, Effect Return or Master section). Effect Send signals of Groups will not be sent to effects that are on a Group section, but they will be sent to Effect Return and Master sections.

Band Effect sidechaining
The Band Effect In input can be used to make your own dynamic noise filters (using a Noisegate or Dynamics effect's expander in the treble band).

Track sidechaining
Track sidechaining can be used to perform "ducking" (i.e. mute background music whenever the announcer speaks, or mute bass guitar every time the kick drum hits). Example: load a Compressor in the bass guitar track, switch it to the Clean program (which supports sidechaining) and select the kick drum track as sidechain input.

The only limitation that applies to Track sidechaining is that sidechains can't "feed" themselves, eg. Track 1 can't use Track 2 as sidechain input if Track 2 uses Track 1 as sidechain input already. This typically isn't a problem in practice.

Some VST plugins can use the right channel of a stereo pair as sidechain input. To take advantage of this you can use a Stereo Effect before the VST plugin, with a Dynamics effect in the right channel effect section. Click the Dynamic effect's Monitor button and select the sidechain input, which will now be routed to the VST plugin. You might want to use another Stereo Effect after the VST plugin to mute the right channel and pan the left channel center.

Effect Send bus sidechaining
This was the only way to do "ducking" until Track sidechaining was introduced. It is rather complicated to set up, but it can still be useful.
Effect Send bus sidechaining is best explained using an example:

Using Effect Send bus as sidechain input

In this example the level of the lower track will be muted when the upper track is loud. The upper track's Effect Send (the rotary knob with the black dot) sends the track's signal to the Effect Send bus. The lower track's output is sent to Group 1. One of this Group's Effect Slots contains a Compressor effect using Effect Send 1 as sidechain input.
Effect Return 1's fader is all the way down in order to avoid sending the signal to the Master section.
In this example the upper track will be audible (the Effect Send is connected post-fader, so the fader can't be all the way down). If you don't want this you can send its output to an additional Group and mute the Group.
The Compressor can be placed in a Band Effect to compress a specific frequency range only.

Note: the Group's Effect Send does not affect the signal sent to the Compressor's Sidechain input, however the signal is sent to the Effect Return section as expected.