What is a Bus in Audio Recording?

There is a term in audio recording that is a bit confusing (go figure) to a lot of folks who are not immersed in in the audio or electronics world.  Oh, who am I kidding?  There are scads of those terms. That is part of the why Home Brew Audio exists – to translate the techno-lingo into the common speech:).

But the term I refer to today is “bus”, also sometimes spelled “buss” or mixer bus, though that just confuses the issue even more. But I digress (Really? Me? but that never happens;)).

Channel strip on a mixer
Channel strip on a mixer

Anyway, the term, as so many are, is a left-over from the analog days when physical mixers were necessary in audio recording (hint: they are no longer necessary in computer recording).  A buss is an output channel on a mixer that has collected all the audio from any channel that is sent to it.  For example, If you have a 16-channel mixer, there will be a channel strip for each of those 16 channels.

The “master” channel is actually a buss, because it takes the output of all the channels on the mixer and outputs them to your speakers or headphones, etc.  All channel strips on mixers are usually sent there by default.  But you can also choose other busses to send these channels to.  For example, there is usually an auxiliary (often abbreviated as just “aux”) buss knob on each channel strip which lets you send the audio on that channel to the (you guessed it) the auxiliary buss on the mixer.  Then the aux buss will output all channels sent to it, and only those channels.

Regardless of how many busses are present on a mixer, there will always be a master-level control somewhere on the  board.  For example, there will be a “master” strip for the master buss, and there will also be a master Aux section (often not a strip, but a section at the top of the mixing board) with an aux output and input and level control.

There are other types of busses and even other names for the ones I described.  For example, sometimes the aux buss is called the effects buss.  But at the end of the day, the only thing you need to know is that a buss combines signals from several other places on a mixing board.

Auxiliary send on a mixer
Auxiliary send on a mixer

We use the same concept on non-physical computer mixers nowadays, which are almost always designed to mirror the way a physical mixer works, though we have a lot more flexibility to create our own virtual busses to create groups, submixes, and any combination of inputs and outputs.

OK Slow Down – What’s a Submix?

You caught me! I just casually used a term like everyone in the world knew what it meant. Mea culpa! I promise to come up with a suitable punishment for myself. But first – the submix thing.

OK, let’s say you have recorded a song with a guitar, a bass, a lead vocal, and 6 harmony tracks (I like to have each harmony part sung twice; so 3 harmony parts will need 6 tracks. I know! Awesome huh?). Then let’s say that I want reverb on all 6 of those vocal harmony tracks. I could go to each track separately, and set up a reverb effect on each one. Well THAT’S tedious! Doing the same thing 6 times.

Wouldn’t it be cool if I could just set up the reverb effect once, and have all the harmony tracks share it? Hint: the answer is “yes!” And that’s exactly what you can do with a buss!

Just create a buss track, set up a reverb plugin effect on it, and then route the harmony tracks through that buss, and they all share like good little harmonies. And…and (this is the best part) you can control how loud all 6 harmonies are with one volume control!

The one on the buss track where they are sharing a reverb (note to the techies – you would want to disable the direct sends from each harmony track to the Master buss first).

What Good Is A Submix?

So now, if you’re listening to the test mix with your wife, and she says (as she always does) “the harmonies are too loud in the mix,” you can nudge them down with one slider/knob instead of trying to adjust the volume on all 6 tracks? One track to rule them all! Now isn’t that useful? It is.

Hopefully this information will allow you to put another seemingly baffling audio term into your vocabulary.

21 comments on “What is a Bus in Audio Recording?”

  1. Thank you for that I am only just getting into recording at the age of 70 so the simple explanation’s are welcomed, still trying to get my head round studio one 3 artist . Thanks again.

    1. You’re welcome Peter! Never too late. And yes, I try my best to explain this stuff in regular-people-speak :-). Thanks for the comment!

  2. Hi Ken, thanks for the to-the-point explanation. Turns out I’ve been using buses for years, but my software and mixer use different terms. Just had the wool pulled off my eyes here!

    This lead me to a question that you scratched upon with “a left-over from the analog days”, but you didn’t say exactly why it’s called a bus/buss. Is that short for something? An old electronic component, maybe…

    Turns out, it’s short for the Latin word “omnibus” meaning “for all” or “for everyone”. It’s why school kids all get on a bus; same as our audio kiddies all grouping into a bus. This, instead of an obscure component or acronym, makes the purpose much easier to remember. Those turkeys calling it a “buss” are just throwing laymen off the trail!

    1. You’re welcome, Paul! Yeah the terms seem almost designed to be confusing. Thanks for your explanation of the derivation of bus/buss. Makes sense since really it just means “grouping.” When working with analog mixers, you had to have that grouping wired in already (unless you knew how to do all the electronics and do it yourself). With digital nowadays, you just decide how you want to group your stuff and just do it. It’s a good time to be recording audio :-).

  3. Hello! I have a Sony MDX-C150 Stereo for a car, and I want to put some sort of aux in so I can play my music from my phone through the car’s audo system. As I was disassembling it, I noticed two L/R RCA jacks in the back marked “BUS IN AUDIO”. Is it possible to play my music to these jacks through an adapter? I still havent tried it as I want the input of someone else before doing so. Many thanks!

    1. Sounds like ti would work. If you got a 1/8th-inch-TRS-to-2-RCA cable and connected it up, it wouldn’t cost you more than about 8 bucks to test this out.

  4. LOVE the layman’s explanations! Thank you for a great site.

    Once tracks are sent to a bus – let’s say 8 drum tracks – they can no longer be manipulated individually, correct?

    In my case, I can do a drum mix and send them to a bus to free up tracks (I’m using a Yamaha AW1600 digital recorder), but I know I’m going to want to tweak the drum mix as instruments and vocals are added to the song. Any suggestions?

    1. Thanks! Once you have rendered or bounced the drum mix down to a stereo pair, you’re right that you won’t be able to manipulate them individually. But doing that to free up tracks is a different thing from using a bus or more correctly for this usage, a submix. The submix bus presumes you have enough tracks to be able to route all drums to a stereo track. Once you do that, you can treat all tracks routed to that destination stereo track the same – i.e. overall gain of the submix (all drums), effects for all drums, etc. If you have that set up, you CAN still manipulate each source track individually to tweak the mix of the drums. So you still have the original tracks for each drum AND the drum bus/submix to work with. If you are trying to free up tracks, you are committing all the source tracks to the destination track(s) and then deleting the original tracks to free them up. In that case you can NOT manipulate the source tracks any longer. You have to get that mix right the first time before doing that “bounce.” I hope that all made sense.

  5. As my fellow “oldie” above, I too (67) am at last reverting to music composition after a long stint of choir directing, and am (still…) building my studio from scratch. And the flood of tech terms is sometimes daunting, although I have a lot of live experience. So THANK YOU for taking the time to explain what I need to understand!!

    1. You’re welcome, Trevor! That is probably my primary goal – to break these things down so non-techies can understand them.

      Good luck in you composing efforts!


  6. Very helpful! At 73 I am still a child in recording— but learning fast with people like you that teach apes how to record!

  7. I cannot stand this term. Bus needs explaining and everyone (except the author of this article) lobs that term at you without even flinching and simply expects every person they say it to, to just understand it. BTW, I don’t think we got ‘where’ the term came from. My guess is that, like an actual bus that picks up multiple passengers, this ‘bus’ can hold multiple ‘passengers’ and take them to the same destination. Can we get the etymology?

    Also, why do sound mixers or anyone who works with a DAW (Digital Audio Workstation) always make it seem like everyone they speak to can mix sound and make songs as effortlessly as they can? “Oh, all you have to do is get your stems, send your buses, count your eggs, up your anti, skim your milk, froth your coffee, weld your axles, and botta bing! You’ve got one of the best-sounding mixes on planet earth!”

    “Oh, THAT is all I have to do? You’re teaching skills are HORRIBLE!” LOL!

    Anyway, thank you Ken for your clarity. You understand what many (most maybe) of us are thinking when we try and read just 2 or three paragraphs of an article about 1 tiny aspect of creating music.

    1. LOL!!! – “Oh, all you have to do is get your stems, send your buses, count your eggs, up your anti, skim your milk, froth your coffee, weld your axles, and botta bing! You’ve got one of the best-sounding mixes on planet earth!”

      Thanks for your kind comment, Justin!

  8. Hi

    My understanding of the term “bus” seems to be different depending on the context. The definition used above that a “Bus” is a channel used to combine and control multiple channels, is correct in the context of a mixer.

    I believe some of the confusion with the term “bus”, stems from the fact that there is a second, different definition for the word “bus” that is used in the context of digital audio. That second definition is that: a bus is a named, software connection between a port (physical input on a sound card) and audio software on the computer.

    In Cubase, when you go to the Menu > Audio > Audio Connections and click “Add Bus”, you are not creating a channel that combines multiple channels at all. What you are actually doing is creating and naming a software connection between a physical port on a soundcard and software on the computer.

    Please correct me if I am in error. My definition of the term “bus” comes from my observation of how it is used in two different contexts.
    • 1. In a mixer (a summing channel)
    • 2. In port to software audio connections (a named software connection)

  9. I saw a console with a buss section. I know what a submux but a buss section, so adjust the inputs there to create a buss, such as a drum bus? I would therefore guess that the number of knobs equals the number of individual channel strips! Right? Wrong? I got my audio engineering degree back in the analog days but we didn’t have this on the quad eight 24 by 24!

    1. The number of knobs? That doesn’t correspond to the number of channel strips. It’s closer to say the number of volume knobs does. but even that isn’t right because a 4 channel (usually 4 channel strips) mixer will have those 4 strips plus the main mix section controlling the master output. So you’d have 5 volume knobs and only 4 channel strips.

  10. Input channels output to a bus, or multiple busses. A bus is a pathway to an output channel. If we wish to hear a lead vocal in both FOH and a foldback wedge, we send it along two busses – to the main LR (via input channel fader) for FOH, and to AUX1 (via input channel send pot for aux1).

    If thinking in terms of an analog board, signal flows vertically through a channel and horizontally along busses. An input can be sent to multiple busses, a bus may contain a mix of multiple inputs, but an output channel has only one bus as its input, and thus we may also refer to the output channel as the bus. Many refer to the main LR as the mixbus.

    Personally, I prefer to refer to output channels as output channels, and use the term bus to denote the signal path by which an input is delivered to an output channel.

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