You are composing your next melody, and after you finished recording all the instruments, you need to apply effects. If you haven’t got a lot of the instruments, you can do it one by one, applying equalizers, compressors, reverbs, delays, and other effects. But imagine you have to deal with 80 tracks, the mixing process will take ages. Not to worry, though, the audio bus will help you save some time as you can apply all the effects needed right here simultaneously to those you already put on the tracks.
Audio bus explained
If you aren’t accustomed to the concept of the audio bus, do not be confused by its name, in all reality, it has nothing to do with a big vehicle capable of transporting a large number of people. Although, there are some similarities hidden within the functionality of those two objects. The audio bus also can carry a lot, but instead of people, we are talking about tracks.
The audio bus is simply an audio track through which you can route other tracks in your project. You can route tracks through an audio bus either in parallel or to group the tracks in order for them to have singular output. Audio buses could be used to apply the same effect to a group of tracks or to run an effect parallel to the dry signal of the audio track to which the effect is applied.
The audio bus could become a very useful and maybe even irreplaceable tool in your audio mixing arsenal. There are a handful of pretty compelling reasons why that might happen. First of all, even if you have the most powerful computer in the world, it still would be a good idea to save some computing power by using one instance of your favorite effect of any kind to affect several tracks in your mix.
Secondly, using certain plugins like reverb and delay or even compressor in parallel might give your mixing workflow some extra flexibility in terms of control. Most of the compressors that you can get your hands on would probably have built-in dry/wet control, which gives you an option of parallel processing, but some of the best digital compressors do not actually offer that option. So in order to run it in parallel, you will have to put it on the new audio track, route signal that you want to be compressed on that audio track, and adjust volume faders according to your preferences.
And, finally, the question of using an audio bus in your mix and project is actually a question of tidiness. Whether it would be your desk or mixing project, a well-organized and coherent working space is halfway to achieving a gorgeous mix. If you are efficient in your workflow and precise in your mixing, you will spend less time and resources, which in turn will let you stay inspired and not to burn out at your work. Actually, you can go even further than that. Using audio buses, you can create templates for your DAW of choice and recall them whenever you feel like or need to record or compose some new material.
How to use the audio bus
Imagine that you are working on a very ambitious and over the top project where a lot of things are going on. Let’s say background vocals complement the lead vocal of this project, and for the sake of argument, there are ten backing vocalists, and each and every one of them recorded their part on a separate track. So if the math is correct, you have ten mono tracks of background vocals. And you panned those tracks and gain-staged them beautifully, but it still needs a bit of compression.
The obvious choice would be to apply your favorite compressor to one of those tracks and copy-paste that instance of the compressor nine more times. But here is the thing, your favorite compressor has some very advanced anti-aliasing algorithms which are very CPU intense, so having ten of those in your DAW will make your computer very unhappy and thus your mixing experience excruciatingly painful. And we are not even considering that there are a lot of other tracks in the mix that may have some sort of processing on them.
So unless you are perfectly comfortable with constantly freezing PCs and crashing DAWs, there is another choice that you could implement. What if instead of ten instances of your favorite compressor, you can use only one? You can create a separate track and route the output of your background vocals through that track.
This will give you, amongst others, two very crucial benefits. Firstly, you can treat all your background vocals as one track and apply all of the processing as you would on a singular track, thus saving your precious time and computer resources. Secondly, it will give you more flexibility options since you can still adjust every background vocal track individually. By simply turning the volume faders, you can decide how much every individual background vocal track will be compressed.
It probably would not be a surprise for you, but not only the background vocals can be treated this way. In fact, you can group any number of tracks using whatever criteria you feel would be beneficial at that moment.
Let’s get back ahead to that slightly over-ambitious project of yours. Imagine that you feel like those background vocals will sound sublime if you put them through some vintage plate reverbs, it seems easy, right? Since you already have a bus that combines all of the outputs of background vocals, just put your reverb there. Well, it is not that simple, actually, if you take into consideration the bigger picture.
What if you have a very strong feeling that your snare and all of the electric guitar parts will also benefit from exactly that plate reverb. Then, you could just route guitar tracks and snare to the same bus, but the problem is there is already a compressor that might not necessarily enhance the sound of guitars and snare. So that means that you are going to use at least three instances of your vintage plate reverb, which is perfectly acceptable, but as you might have guessed, there is another way to do it.
An auxiliary channel is an audio bus that is used to route tracks in parallel. To put it simply, you can create a separate audio track and insert your plate reverb in that track. You can then route every track that you need to have a vintage plate reverb effect on through that separate audio track. This means that you have both your original unprocessed background vocals, snare, guitars and one stereo track with all of those instruments affected by a reverb. It is then just a question of adjusting volume and sending faders to get a perfect balance between dry and wet signals and the overall level of reverb.
If by any chance you have some hardware gear that you use to record audio material, using auxiliary channels will let you to have more control and flexibility in terms of reporting. For example, you can record vocals completely dry, then send the recorded track to the hardware compressor and route the return signal of the compressor to the separate audio track.
This may sound a bit complicated, but in reality, it is relatively easy to do, not to mention that it gives you a whole other level of mixing options. Without the auxiliary buses, if you made a mistake while adjusting your compressor, you would have to rerecord that part again. Using the auxiliary buses with hardware compressors relieves you of this possibility since the hardware compressor runs parallel in real-time. And if you feel that the settings are wrong or at least not quite right, all you have to do is simply adjust the knobs on your compressor without any rerecordings needed. The same goes for just compressors and every out of the box hardware gear like reverbs, delays, and tape machines.
Summarizing all written above, the audio bus is a very useful and irreplaceable thing as it can not only save the power of your CPU but also lighten the process of applying desirable effects. It does not matter which effects you want to apply, whether it is reverb, delay, or compressor, what is important is that the audio bus lets you put them in parallel only if you put it on a separate track. Those who are pedantic and prefer that everything around them would be in a specific easy-understandable fashion will find an audio bus a very handy thing.