Aux tracks are an incredibly flexible tool used in music production. Amongst other applications they are used commonly to create submixes, parallel effects sends and monitor mixes. Read on for some quick+dirty theory plus a demonstration on setting up parallel effects in Pro Tools.


Pre/Post Fader Sends?

Sends can be configured to be Pre-Fader or Post-Fader. In the case of pre-fader sends the send level isindependent of the channels main fader which means the main fader level does not affect the send level. Pre-fader sends are best used for setting up headphone or monitor mixes.

Post-fader sends do exactly the opposite and are ideal for parallel effects as they maintain the relative levels of effect and recorded signal. By default sends are set to post-fader. When using parallel effects it is essential that the mix control (sometimes labelled wet/dry) is set to 100% wet as you only want the effected signal passing through the aux track, this also avoids phase cancellation that may occur.

Signal Flow

In the case of a parallel send, the aux track acts as an additional fader which controls the overall level of a specific effect. Many effects may be applied this way with the most common being reverb, delay, compression and saturation. The aux bus may be named the effects return as an amount is being sent by the individual track send to the aux track which is returning the now effected signal back into the mix.

For the visually inclined, the diagram below illustrates the signal flow from each tracks send to a reverb bus and then back into the reverb aux return. (Credit to the free Intro to Music Production Berklee course for the diagram).

Reverb Signal Flow

Parallel effects allow you to conserve processing power (only one instance of the plug-in) and create the illusion of a space (in the case of reverb) by applying varying amounts of the same reverb to numerous tracks.

Using Parallel Effects in Pro Tools

For this example we will be creating a reverb send. To best demonstrate this principle, open up or download a Pro Tools session with at least two different audio tracks.

  1. Create and name a reverb bus.
    – Setup -> I/O -> Bus
    – Click on an available bus and rename it “Reverb Bus”
  2. Create and name an aux track.
    – Track -> New
    – Select stereo (delay effects are typically stereo effects) and select aux track
    – Name the aux track “Reverb Aux”
  3. Set the Reverb Aux input to the “Reverb Bus”
  4. Place a reverb effect on the Reverb Aux track using an insert.
  5. Insert a send on one of the audio tracks and route it to the “Reverb Bus”
  6. Adjust the send level on each individual track. This varies the amount of signal being sent to the reverb aux track and thus the amount the track is being affected.
  7. Ensure the send is set to Post-Fader.

Keyboard Shortcuts and Tips

  • Create New Track: Ctrl + Shift + N
  • Bring send level up to Unity Gain: Alt + Click send fader
  • Setup Mini Send Faders:
    a) Via Mix Window: Windows + Click on the send
    b) Via Edit Window: Views -> Sends A-E – Send A
  • Send Reverb to all tracks: Hold down Alt while inserting a send on one of the tracks
  • Engage solo safe on Aux Returns (allows you to solo the tracks being sent to it): Ctrl + Click aux solo button.