What are Aux, Sends, and Returns? – Signal Routing in The Box

What are Aux, Sends, and ReturnsAuxes, busses, sends, returns. Music talk can be pretty cryptic.

In the world of signal routing, it’s easy to get tangled. Let’s save you the hassle, and get you started on your road to successful signal routing by answering the question “What are auxes, sends, and returns?”

Open up your DAW of choice, and get ready to explore!

Defining Signal Routing

The three terms we will be decoding today (aux, sends, returns) all have to do with signal routing. Signal or audio routing is the process of mapping signals to separate tracks in order to add desired external effects.

For example, one might route a vocal track to a separate auxiliary track containing reverb. This allows the producer more control when mixing. Since the sound is routed to a different track as opposed to being directly on the vocal, the engineer is able to dial in the precise amount of reverb he/she desires, allowing for more options, and different sounds.

Signal routing also allows for certain sounds to be grouped together. Oftentimes, engineers like to process their drums in similar ways, so instead of applying the same effects on every individual track, they can save time by routing the tracks all on one channel. In every DAW, audio routing is essential to efficient and precise results.

Aux, Sends, Returns Defined

Before applications, let’s gain a firm understanding of each term at its core. These integral parts of signal routing existed long before DAWs, and are essential to the vocabulary of every serious producer.


In order to understand Aux, Sends, and Returns, we must first define bus. Bus is a general term used to signify the routing of tracks to a singular channel. The most common example of a bus is the “Master” channel, which consists of all the tracks routed to one signal, otherwise known as a bus.

Another common example of a bus would be a drum bus, where all percussion sounds are routed to one channel so that the percussion elements can all be processed in a similar fashion. Busses can be routed to even larger busses, making signal routing limitless.


Aux-send layoutAux, short for auxiliary, is a bus used to create external, precise mixing. Aux channels do not have instruments/sounds on them. Sometimes they are referred to as effect channels, as they are merely there to be routed to.

Aux channels can be broken down into two parts: Sends and Returns. Auxes are useful because they allow for the original sound to run parallel with the processed sound. A mixer chooses how much of a particular signal he/she wants to send to the Aux channel. In Ableton, two Aux channels (Titled A and B) are created by default. Aux channels are great for filtering in effects such as reverb and delay.


The send is the input part(s) of an Aux channel. It typically rests on the track of the actual sound(s), and is used to dictate how much of the sound should be sent to the Aux channel to then be processed.


The return is the fader that determines the levels of the Aux channel, or the amplitude of the sounds after passing through the Aux bus. It is usually on the Aux channel itself. You can think of return as the output of the Aux track.

General Uses

Ultimately, signal routing is merely a tool used to unleash an unlimited amount of melodic possibilities. However, there are a couple of common uses that come up in everyday mixing, so it’s important to be aware of them.


The most obvious and common use of signal routing is creating groups. Groups not only allow for better organization within a project, but make it easier for an engineer to avoid clashing frequencies. For example, it is not uncommon for a mix to be routed into low, mid, and high-frequency groupings before the final mastering process. With a simple EQ on a group track, the producer can single out which frequencies need to be reduced or amplified.

Parallel Compression

Parallel compressionParallel compression is created by routing signals to an Aux track and adjusting the sends to your liking. The idea behind it is that it allows the mixer to have more control by simultaneously running the dry signal with the processed audio coming from the return track of the aux or bus. Parallel compression is great at preserving dynamics while still keeping tracks cohesive. It is commonly used with vocals and drum groups.

Read more about parallel compression.

Live Performances

Signal routing allows for DJs, singers, and producers alike to have dynamic and captivating performances. Since auxiliary tracks allow for effects to be separate from an initial signal, a performer can quickly turn a send or return knob to produce a new sound for a precise duration. Sends and returns streamline the performing process, and allow the user to focus more on the moment, rather than technical difficulties.

How to Setup Signal Routing

There are infinite ways to implement signal routing. To get us started, here’s a general guide on the setup of 3 of the most common applications.

Grouping setup

Determine what you’ll be grouping. Common groups include vocals, drums, and tracks grouped by frequencies (Low, Mids, Highs).

  1. Select all of the tracks. In Ableton, this can be done by selecting/clicking on the tracks while holding down the shift key.
  2. Right-click to select “Group Tracks”, or control G in Ableton.
  3. The heading track or the track above all of the grouped tracks, is the new bus. All of the tracks are routed to this bus, and will be affected accordingly.
  4. Use the bus to apply effects, EQs, and variants of your choosing.
Parallel Compression setup

Insert an auxiliary track. In Ableton, these are here by default under tracks “A” or “B”. Make sure the auxiliary track is completely clean without any effects. Defaults often come with either reverb or delay, two effects seen often with parallel compression. They can be removed by selecting the effect within the auxiliary track and pressing delete.

Place the desired effect onto the aux track. If there is a dry/wet knob, turn the knob to 100% wet, since you will be toggling the amount of the effect through the send.

Go to the signal track that you would like to use parallel compression with.
Slowly adjust the send knob with the audio signal playing to determine how much of the processed signal you would like in proportion to the dry track.

Adjust the return knob on the auxiliary track to increase/decrease amplitude.

Read more about how to set up parallel compression here.

Live Performance

Decide which effects you would like to have for performance preemptively. Consider the common options of reverb, delay, chorus, and vocoder effects.

Create auxiliary tracks, placing one or more of the desired effect(s) on each.

Map the sends and/or returns to your external controller. In Ableton, this mapping can be done by pressing control M, turning the desired knob, and selecting the send/return you are trying to map the knob to. To save your mappings, simply press M again, and then test to make sure the map has been routed.

Experiment with live automation. Live signal routing with an external controller allows us to gain a physical understanding of how the different parts of a DAW are connected. The more intricate the mappings, the more you’ll learn!

Alternative/Creative Uses

Again, the possibilities created with auxes, sends, and returns are endless. Here are some more uncommon uses that might not be the first thing to come to mind.

Creating a fuller mix

An aux bus paired with reverb/chorus/flanger effects and some creative panning can instantly widen your mix and dry signals!

  1. To do this, take the sound of your choosing and pan it all the way to the left or right.
  2. Route this track to an aux track.
  3. Place the desired effect onto the aux track, making sure the wet is set to 100% if applicable.
  4. Finally, pan the aux track all the way to the left or right, making sure it is in the opposite direction of the dry signal (For example, the dry signal is fully panned to the left while the aux bus is fully panned to the right).

Adjust sends/returns accordingly. This fun effect will make your mixes sound larger and fuller. Try experimenting with different panning/effect ratios!

Chain effect control

Another benefit of using aux busses as opposed to putting the effect directly on the signal track is that you can layer multiple effects and/or have more control over the effect on the aux bus. For example, if you notice that a certain frequency is producing an abrasive hum when using chorus, but not while using delay, you can set up two separate aux tracks with each effect and cater them appropriately. The chorus aux can be equalized while the delay aux remains untouched.

Final thoughts

Signal routing allows for limitless control and possibilities with your projects. These common yet essential techniques are great for polishing your sound, creating inventive sounds, or simply organizing your tracks! Make proper signal routing a part of your mixing ritual.