External Sidechain Routing

All version of MultitrackStudio feature "internal sidechaining". In this scenario an effect (typically an EQ) can be inserted in the sidechain, while the sidechain input is always connected to the effect input. The Pro Plus edition also features "external sidechaining", where the sidechain input can be connected to sources outside the effect.

Sidechain section

The Compressor, Dynamics and Noisegate effects, as well as some VST plugins, feature sidechain inputs that can be connected to various signals:

• Internal: the effect's input.
• Track: the output of another audio or soft instrument 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 In: the Band Effect's input (available if the effect is in a Band Effect).

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.

Band Effect sidechaining

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

VST Plugin sidechaining

VST effect plugins which have more than 2 input channels will get a Side Chain box just like the one in the Dynamics/Compressor/NoiseGate effects. Input channels 3 and 4 will receive the sidechain source signal.

VSTi plugins which have audio inputs get a Side Chain box as well. You can, for example, load vocal pitch correction plugins in an instrument slot and route the vocal track to it using the Side Chain box. Now you can use the track's MIDI editor to enter notes which the plugin can use to determine the correct pitch.

Some VSTi plugins have more than 2 output channels. The outputs of these plugins are available as sidechain sources. Up to 15 outputs per VSTi plugin can be used a sidechain sources. These sidechain sources can be stereo, unlike all other sidechains which are mono. This feature is especially useful with drum plugins. You can, for example:

• Use the kick drum channels as sidechain source for a Compressor or Dynamics effect in the bass track.
• Route the plugin outputs to tracks, so you can mix the drum instruments in the main window instead of the plugin's Output Mixer. A VSTi output can be routed to a track by adding an audio track and loading a Dynamics effect in its first effect slot. In this Dynamics effect you can select the sidechain source and click the Monitor button. If you route all the drum VSTi outputs to tracks this way you can use the VSTi track's Mute button to mute it. Note that you'll have to unmute this track if you want to play the VSTi live, or in order to hear notes when clicked in the track's editor. This is because the sidechains only work when the track is playing back.

Some VST plugins come with proprietary sidechain input plugins. This is a secondary plugin that picks of the sidechain source and routes it the the primary plugin. This setup can't work without glitches in MultitrackStudio on multiple CPU machines. If you rightclick a VST plugin in an effect/instrument selector you can check the "Has sidechain input plugin" option. New instances of the plugin will now get a Sidechain Plugin box. This box is identical to a Side Chain box, except that its output is ignored. You can load the secondary plugin in the effect slot and choose the sidechain source. Now MultitrackStudio's sidechaining mechanism will make sure it works OK under any circumstances.