Bussing is routing several tracks to a shared destination so you can treat them as one. A bus is a channel that other tracks feed into, so you can level and process a whole group of them together. An aux send is a slightly different move: it routes a copy of a track to a shared effect, like one reverb, so several parts can share the same space. Both are just routing.
None of this is tied to one plugin or one DAW. The names differ between programs, so a bus might be called a group, a subgroup, an aux or a stem, but the idea is the same everywhere. The numbers and habits below are common starting points rather than strict rules.
A bus is a channel that several tracks are routed into so you can treat them as one. Instead of every track running straight to the master on its own, you point a handful of them at a bus first, and then that single bus channel carries them onward. It gives you one fader and one set of plugins for the whole group.
Think of the default path in any DAW: each track outputs to the master, and the master is the sum of everything. A bus sits in the middle of that path. You change the output of your kick, snare, hats and toms so they all feed a channel called Drums, and now the Drums bus is where all of that audio meets. Move its fader and every drum moves together. Put a plugin on it and every drum passes through that plugin.
That is the entire idea, and it is worth keeping simple. A bus does not change how anything sounds by itself. It is just a meeting point you route audio to, so that a group of related tracks can be handled with one control instead of ten. What you do at that meeting point, the levelling and the processing, is where the value comes from.
Different programs use different words for the same thing. You will see bus, group, subgroup, aux, stem and FX channel depending on the DAW, and they overlap. When a name is unclear, ask the practical question instead: does this channel carry the whole signal of the tracks, or only a copy sent to an effect? That distinction matters more than the label.
A subgroup, also called a group bus, is a bus that carries the full signal of the tracks routed into it, so it takes over their path to the master. The individual tracks stop going straight to the master and go through the group instead, which means one fader now controls the whole section and one chain of plugins processes all of it at once.
The everyday example is a drum bus. You route the kick, snare, hats, toms and overheads to one Drums group, so their direct outputs to the master are replaced by a single output from the group. Now you can pull the whole kit up or down with one fader while the internal balance between the drums stays put, which is far easier than nudging six faders in step. The same works for a Vocals group, a Guitars group, or a bus for a whole section of an arrangement.
Because the group carries everything, any plugin you add there acts on the sum of the parts. A common use is one gentle compressor across the drum bus, set for just a dB or two of gain reduction, so the kit starts to move and breathe as a single performance rather than separate hits. People call that glue. You could also EQ the whole group, or drive it a touch for weight, and it lands on all the parts together.
One thing to watch is level. As parts stack onto a group their levels add up, so a bus tends to run hotter than any single track feeding it. Keep an eye on the group meter and pull its fader down if it is creeping toward the top, which is the same headroom habit covered in our guide on gain staging.
An aux send routes a copy of a track to a shared effect, so several tracks can feed one reverb or delay and share the same space. The original track keeps playing on its own channel at full level, and the send is an extra tap off it that goes to a separate return channel where the effect lives. You are branching a copy, not moving the whole signal.
Say you want reverb on your vocals, guitars and a synth. You could put a separate reverb plugin on each of the three channels, but that spends CPU three times over and puts them in three slightly different rooms. Instead you create one return channel, often called an aux return or an FX channel, and load a single reverb on it. Then you turn up a send on each of the three tracks so a copy of each feeds that one reverb. All three now sit in the same space, you have one reverb to tweak rather than three, and you save CPU.
The effect on the return is usually run fully wet, because the dry sound is already coming from the original channels. You blend the wet return underneath the dry tracks with the return fader, so you are mixing an ambient copy in behind the direct sound rather than replacing it. This parallel, blend to taste behaviour is what makes sends so handy for reverb, delay and other space and texture effects.
A send can tap the signal before the channel fader or after it. A post-fader send follows the fader, so as you pull the dry track down its effect drops with it and the balance holds. That is the usual choice for reverb and delay. A pre-fader send ignores the fader, so the amount going to the effect stays fixed even if you mute or drop the dry track, which is useful for headphone mixes and for effects you want to hold steady on their own.
Use a group bus when you want to control and process whole tracks together, and use an aux send when you want several tracks to share one effect while keeping their own dry sound. The difference comes down to what travels down the channel: a group bus carries the whole signal and replaces the direct outputs of the tracks, while an aux send carries only a copy that is blended in parallel with the dry.
So if the job is levelling and shaping a section as a unit, drums that should move as one kit, backing vocals that should sit at one level, reach for a group bus. If the job is placing several parts in a shared effect, one reverb for the whole mix, one delay across the lead parts, or a squashed copy blended back under a track, reach for a send. Sending a copy to a compressor and blending it under the dry is exactly the trick covered in our guide on parallel compression.
| Behaviour | Group or subgroup bus | Aux or effect send |
|---|---|---|
| What travels down it | The whole signal of the tracks you route in | A copy of the track; the original keeps playing |
| Routing | Replaces the direct path, so tracks feed the bus and the bus feeds the master | Runs in parallel, so the dry track still plays on its own channel |
| How it blends | Serial, so anything on the bus acts on the whole group | Parallel, so the wet return is mixed under the dry to taste |
| Common job | Level and process drums or vocals together, like glue compression on a drum bus | Share one reverb or delay across many tracks, which also saves CPU |
A few routing habits keep either one tidy:
A group bus is for handling whole tracks as one, and it replaces their path to the master. An aux send is for sharing one effect across tracks, and it is a copy blended in parallel with the dry. If you are levelling and processing a section, that is a bus. If you are feeding several parts into one reverb, delay or parallel effect, that is a send.
Bussing is a mixing habit. It only matters once you have parts worth mixing, and writing and recording those is the harder job. The routing on this page is simple to set up; having clean parts to point it at is the work.
The Collection is our three instruments together, ARGISH, SILT and REHEAT, with three separate licence keys. This page is about grouping and routing parts, and that stays tidy when the parts going in are already clean and separate: each instrument gives you a clear, controlled sound on its own channel, so grouping and sending them stays simple instead of a tangle. ARGISH is a self-playing drone synth, SILT is a tape-loop instrument, and REHEAT writes acid lines, and whatever you make with them is yours to release. Each one ships as AU, VST3, AAX and a standalone app on macOS, signed and notarized, and a VST3 on Windows.
You can hear one free in your browser first, no install and no account, then decide.
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