What Are Subgroups? (Audio Mixing, Recording, Live Sound)


Subgroups are an important routing tool in our mixers, allowing us to simplify the mixing process and get more out of fewer processors and effects. Whether you're mixing a record, recording, or mixing live, using subgroups can help enhance your workflow and get you better results. If you're unsure about what subgroups are or want more information on how to utilize them in your mixes, you've come to the right place!

What is a subgroup in audio? A subgroup is a mixer channel fed by a group of tracks/channels combined onto a single bus. Similar tracks are often grouped together (i.e., drum tracks bussed to the drum subgroup). A subgroup offers control over its grouped sources, often with inserts, sends, pan pot and fader, and output routing.

That's my concise answer, though we'll be diving deeper into subgroups throughout the rest of this article.


A Brief Primer On Signal Flow

Before getting to subgroups, I want to briefly discuss signal flow, particularly in mixers, to give a better idea of how signals flow to and from subgroups.

Mixers are made of channels or tracks with inputs (audio is routed into the channel/track) and outputs (audio is routed out of the channel/track).

Audio track inputs can be microphones, instruments, recorded audio, or other playback sources.

An audio signal will flow into an audio track through its input and generally pass through a preamplification stage. From there, the track/channel may have built-in processing (typically semi-parametric EQ) and/or insert points where other/external processes and effects and be inserted in-line. If processing is to be done, the audio signal will flow through these processors before moving on.

For more info on inserts, check out my article Audio: What Are Inserts? (Mixing, Recording & More).

From there, we typically have our sends, which carry the audio from the channel through a bus to an auxiliary track. Each send has its own gain control to effectively move the signal to its aux track without affecting the main signal flow toward the original channel/track output. We can imagine a send as “splitting” or “duplicating” (though these terms aren't technically correct) the signal to move it to additional locations in the mixer.

Aux sends send the audio to aux tracks, which can be used for alternate monitor mixes, effects returns and parallel processing. The send levels can be set as pre-fader (independent of the channel fader position) or post-fader (dependent on the channel fader position).

To learn more about aux tracks, check out my article Mixing/Recording: What Are Auxiliary Tracks, Sends & Returns?

Moving on, we have the pan pots and fader to control the track's position in the stereo panorama and its level in the mix, respectively.

Finally, we get to the output of the track/channel. By default, the output is generally the mix bus, which routes the audio to the main mix. However, we can often change the output(s) of the tracks to a different bus and have that bus feed the input of a subgroup instead. From there, the subgroup channel typically offers the same signal flow and can be outputted to the main mix (ultimately).

So that covers the basics of mixer signal flow and where subgroups come into play. With that primer, let's move on to defining subgroups in greater detail.


What Are Subgroups?

As mentioned, a subgroup is a channel fed by a group of tracks/channels combined onto a single bus. A subgroup offers control over its grouped sources, often with its own inserts, sends, pan and fader controls, and output routing.

In analog mixers, which are inherently limited by hard patching, the subgroup channels are generally laid out between the audio tracks/channels and the main outputs. The outputs of the tracks can then be routed to whichever subgroup is available, often selected by a push button.

This is done virtually in digital mixers and digital audio workstations, and DAWs often have tremendous flexibility when it comes to routing to and from subgroups. We can select from a much larger number of buses at the track output and set up more subgroups if we please (relative to analog hardware mixers).

In many digital systems, the subgroups will be set up on auxiliary tracks, which means the terms often overlap. Usually, when the subgroups are hardwired, they're referred to simply as subgroups. When we have the great flexibility and versatility of a DAW, the subgroups are typically set up by the user on “auxiliary tracks”.

Either way, these subgroups act as bus destinations (they are fed by a bus at the input). These buses are typically stereo or dual mono as the subgroups, themselves, are usually stereo.

So we set the output of a track to a specific bus, and that bus routes the audio to its subgroup.

When it comes to routing multiple tracks to a subgroup, the tracks are most often, though not always, grouped by their similarities. For example, all drum tracks are bussed to the drum subgroup, and all the background vocals are bussed to the backup vocal subgroup.

With subgroups set up properly, we can effectively combine the different groups of instruments together and process and mix the audio in groups rather than in individual tracks. This offers a simplified, more top-down approach to mixing, allowing us to do more mixing with less processing.

Some confusion comes about in the terminology. In practice, we often call our subgroups by the name of the bus feeding them, i.e., drum bus, guitar bus, vocal bus, etc. When doing so, we often reference the subgroup channel on the mixer or DAW rather than the audio conduit that carries the audio signals themselves.

So if we want to be technically correct, it's better to call these “buses” subgroups. However, the point still comes across.

For more info on using bussing in your mixes, check out my YouTube video here.

For more information on buses, check out my article What Are Audio Buses? (Mixing, Recording, Live Sound).


Using Subgroups

Now that we understand what subgroups are and their main benefits, let's consider how to use them in practice.

The goal of mixing, put simply, is to achieve balance. This means balance between the levels of the tracks and balance within the space of the mix (depth, width and height). It also means having a sense of separation and cohesion between the elements, as contradictory as that sounds.

So before we reach for mixing with subgroups, it's always best to get a rough mix with the individual audio tracks. These tracks give us intricate control over the balance between elements essential to a great mix.

I'd advise starting by setting up proper gain staging across all tracks and spending some time adjusting faders (and even pan pots) to get a rough mix with just the level and panning balance. It can be advantageous to collapse/sum the main mix to mono for this purpose to maintain mono compatibility in the original balance of the mix, even if you're panning as you go.

As an additional point, I'd also recommend high-pass filtering low-end noise from tracks at this time as well.

I have videos on gain staging and mono compatibility that you can check out by clicking the links in this sentence.

To learn more about gain staging, mono compatibility and high-pass filters, check out the following My New Microphone articles:
Mixing: What Is Gain Staging & Why Is It Important?
Mixing: What Is Mono Compatibility & Why Is It Important?

Audio EQ: What Is A High-Pass Filter & How Do HPFs Work?

From there, we can group our tracks together into their proper subgroups, assuming your mixer has that capability. All modern DAWs worth their salt will have flexible bus routing to set up subgroups (though the terminology may differ depending on the brand).

Related article: Top 7 Best Digital Audio Workstations (DAWs) On The Market

So we can group similar tracks together in their own subgroups.

Of course, we don't necessarily have to group multiple tracks together in a subgroup, though that's the main benefit. As a matter of mix organization, it can be advantageous to bus all our tracks to subgroups even if we aren't taking advantage of the grouping aspect of subgroups. This is often the case with single bass guitar tracks or single lead vocal tracks.

Once the subgroups are set up, we can begin by adding a mix bus compressor on the main stereo output channel (if you'd like) before moving on to processing the subgroup channels.

This “top-down” approach allows us to get bigger wins more quickly with fewer hardware units or plugins. We use the subgroups to process multiple tracks together with single processors rather than having to process each individual track.

Here are some examples, to wit:

  • Cut out a resonance in the drum room by EQing the drum subgroup as a whole.
  • Saturate all bass elements/tracks for improved midrange clarity and grit by saturating the bass subgroup as a whole.
  • Glue the background vocals together and push them behind the lead vocal in the mix by compressing the backup vocal subgroup and inserting a high-shelf cut EQ.
  • Bring up the presence and reduce the muddiness of the keyboards by EQing the keyboard subgroup.
  • Duck the electric guitar to reduce competition with the lead vocal when both are present by inserting a compressor on the electric guitar subgroup and setting the lead vocal track (or subgroup) as the compressor's sidechain.

Beyond processing the subgroups themselves, we can also typically send audio from our subgroups to auxiliary tracks for alternate mixes, effects returns, and parallel processing.

A few examples to note here could be:

  • Bring all the drums down and turn all the vocals up in the vocalist's monitor mix (for headphones, in-ears or foldback monitors) during live performance or recording.
  • Send all the drums to an aux for parallel compression.
  • Send all the vocals to an aux for parallel saturation.
  • Send different amounts of each subgroup to a reverb effect return (aux track) for more control over the space.
  • Send different subgroups to different delay effect returns (aux tracks) for more intricate delays in the mix.

Once the mix is largely taking form, we can get more intricate at the individual track level to fix specific issues.

Of course, these are just my suggestions. Work however you like to work to get the results you're after in your mixing and recording.


This article has been approved in accordance with the My New Microphone Editorial Policy.

Arthur

Arthur is the owner of Fox Media Tech and author of My New Microphone. He's an audio engineer by trade and works on contract in his home country of Canada. When not blogging on MNM, he's likely hiking outdoors and blogging at Hikers' Movement (hikersmovement.com) or composing music for media. Check out his Pond5 and AudioJungle accounts.

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