What Is An Aux Bus ?

You’ve probably come across the term Aux track before …when dealing with audio mixing.

It is quite a popular term and most audiophiles know what it exactly means.

Another term that you’ve probably come across is what is called a “bus” e.g reverb bus, delay bus and so forth.

These are very important concepts in audio production and it pays to know what they mean.

In this post I’m going to take you into what an Aux Bus is so you know them better and know how to use them.

Without wasting a lot of time, let’s get into it…

So, what is an aux bus ?

An aux bus or an auxiliary bus is track where variable audio signals are routed for effects processing. An alternative definition of an Aux bus is where feeds from various channels are brought together to be routed to an external processor (like an effects unit) or monitor send.

Aux tracks really don’t record any audio. However, they are used as a track meant for effects.


In audio engineering, a bus sometimes written as buss is a signal path that is usually used to combine individual audio signal paths together.

It is used mainly for grouping several individual audio tracks which can be then manipulated, as a whole, just like you would an individual track.

This grouping can be achieved by routing the signal physically by ways of switches and cable patches on a physical mixer, or by using routing features that can be found on a digital audio workstation.

Using busses allows sound engineers to work a lot more effectively, precisely and with better consistency,

A bus is simply a point in a signal flow where multiple channels are routed into the same output.

In music production we usually have different instrument groups that are often bussed and processed together to make them sound cohesive and consistent.

Most songs usually have a drum bus, instrument bus, and vocal bus.

The master channel in your DAW is also basically a bus.

 This is why it sometimes called the master bus.

All of your track outputs merge together before leaving your DAW through the master bus.

The Benefits of Using Aux Sends and Buses

There are various benefits that coming with using Aux sends and Buses and I’ll discuss some of these below.

CPU Load

Having multiple channels with the same reverb or delay or whatever plugin is a lot not only for your CPU but for your RAM as well.

Of course, if you’re working with a highly optimized computer that can handle this kind of load without lagging or crushing … you may not really see this as a problem.

But there’s really no need for you to be running the same effect plugin with similar or almost identical settings on every track When you can simply use routing.


Having all your mix elements grouped and using an effects track to process them will give you a more unified results rather than having various settings and parameters on different audio.

For example, sending all of your drum tracks to the same reverb or giving multiple tracks the same delay can keep your mixes consistent, coherent  and have your mixer well organized.

Processing abilities

Using an aux to run your effects allows you to process that affected signal a lot further.

This provides you a great opportunity to enhance and clean up your mix.

For example putting an EQ on your reverb return can help amplify the crack of the snare.

Boosting the EQ at various point offers you so much control over the reverb. Control that you wouldn’t have if you simply slapped it directly on a mixer track.

You can also experiment with stacking multiple reverbs to achieve a sound that is unique to your mix.

Parallel Processing

Sending a track to a bus also opens up the option for parallel processing, most often used for drums and vocals.

Parallel processing can allow you to have more control over the output of your signal.

In parallel processing you basically have a dry track and a heavily processed copy of that track.

The heavily processed track will obviously not sound good on its own which is you need to layer it with the dry signal.

This allows you to preserve the integrity of the dry signal and simply rely on its processed copy for effects.