Considerations when using master bus processing in your mix, before mastering

By Rob Stewart - - Apr 30, 2017

Last updated on July 22, 2017.

I often get asked if adding processing on the master mix bus is a good idea or if it creates problems for mastering engineers. This is a contentious issue for recording artists and engineers. Everyone has a different perspective, and there is technically no “right” answer here. I will give you my perspective on this, and my reasoning. Note that bus processing in general is an essential creative tool. My intent for this article is to focus on master bus processing, particularly when you are considering having your mix mastered.


My philosophy: The further you go back, the more flexibility you have…

To address mix issues, I prefer to go as far back to the source of a problem as possible. That is how I’ve found that I can make the biggest difference for my clients, helping them achieve the best results. It is as simple as that. If a problem is a “recording problem”, or a “mix problem”, I prefer to tackle the problem at the source. Adding more processing at the end stage such as the master mix bus or even later on at the mastering stage may help a little, but the further you go back in the production process, the more flexibility you have to solve problems. That’s why I recommend that a recording engineer work to achieve their desired results at the recording stage, and a mix engineer work to achieve their desired results within their mix.


Does master mix bus processing cause problems for a mastering engineer?

No, it will not cause problems if everyone involved communicates. Some mastering engineers may ask you to provide different versions of your mix (with and without master bus processing on). That can be helpful in certain situations to allow the engineer to hear a "purer" version of your mix, before all the end stage processing was added. Bus processing can create new problems for a mix that the artist is not aware of, and it can make it challenging for a mastering engineer to troubleshoot issues if they are not aware of what bus processing was used. For example, is the issue I’m hearing caused by something inside your mix, or is it caused by something applied to your mix? Sometimes the answer is obvious but communication makes that troubleshooting process much easier. 


Know what you are trying to do, or which problem you are trying to solve

Some artists feel strongly that they need a certain amount of bus processing to create their signature sound. I would never question that approach because it’s an artistic choice. It is absolutely fine until there is an issue that needs to be addressed. I call out mix issues as I hear them, and then the troubleshooting process begins. For example, how was the track recorded, what processing was used on the track, was there any on the mix bus, or sub-mix buses?  As long as everyone is sharing information, bus processing alone cannot ruin a mix. Poor communication could, though! So it is important that an artist or mix engineer carefully consider what they are attempting to do or solve by using bus compression, in case there are questions at the mastering stage.


My thoughts on common mix bus processes

Master mix bus equalization – less effective than addressing elements within your mix

If a mix sounds overly dull to me, I determine which elements of the mix are making it sound that way and suggest ways to resolve that (e.g. add more top end to the vocal, brighten the guitars etc.), rather than suggesting that the artist EQ the whole mix. EQ’ing your mix will change all the other tracks in the mix that already sound fine (fixing one thing while breaking another). For example, if you brighten a mix to help the vocal or the guitars, you may be adding too much top end to the cymbals. But dialing back the top end again will only dull the vocal. Then what?


Master mix bus limiting for gain – not needed when you plan to master your mix

There are technical issues to consider with limiting. Limiting will not usually affect tone unless it has been applied so heavily that it audibly distorts a track. Limiting allows you to raise the gain of a track or a mix, but there is a cost. Even small amounts of limiting will add distortion, and distortion accumulates throughout the production process. Gain is not the main focus at the mix stage. The mix engineer focuses on other aspects such as energy, perceived loudness, depth, clarity etc. Limiting can be effective on certain tracks within your mix (drums, for example) but I do not recommend limiting whole mixes if you plan to have them mastered, because the mastering engineer will also apply limiting at the end stage of the mastering process. If we both limit your mix, we are doubling the amount of distortion caused by limiting.


Master mix bus compression – beware that it can add glue, and gunk too

Compression is finicky because a less experienced artist may apply compression and not notice all of what it is doing. Especially if it is fast compression because nearfield monitors often will not reveal dynamics in a detailed enough way for the artist to spot a problem. A worst case scenario is someone who is using compression both in their mix, and at the bus level, and creating problems that they are not hearing because of their monitoring.  If you are finding yourself compressing your mix for “glue”, consider digging deeper into arrangement and other aspects of your mix in case there is an alternative.


Master mix bus multiband compression – compression on steroids

Multiband compression is widely underestimated, misused and misunderstood. It is a sledgehammer when often times only a tack hammer is necessary. Instead of one basic compressor, we have an army of anywhere from 3 to 32 bands depending upon the processing tool. Love them or hate them, it goes back to whatever I hear when I listen to your mix. If I hear a problem, I will call it out. I may not immediately know that the issue is caused by multi-band compression, but I discuss what I’m hearing with you. If multiband compression is causing an issue, you don’t necessarily need to remove it. Maybe we just need to adjust the settings. If you’re using multiband compression to fix an issue, we can dig deeper to see if there’s a more effective option.


Master mix saturation – from grit and grunge to blur and fuzz

Saturation of any kind - tape, tube, transformer or anything else can be a big problem if it is applied to a whole mix. It is much like reverb where you can easily overdo it without noticing. It is cumulative. In that sense, applying it on the master bus could be safer than adding it to every track in your mix, because it won't "build up" within your mix. It still requires careful monitoring because too much saturation blurs all the important details of a recording. Blurring detail is fine if that is your goal, but I will mention it if I think a mix has too much distortion, to the point where I feel it is causing damage.


Master mix Mid/Side processing – be aware of what actually creates width in your mix

I won’t go into too much detail here. Mid/side processing can be effective for some things, but it can also create issues. It goes back to what are you trying to solve. You can find much more detail in my articles, here:


A final thought – using master mix bus processing is fine (everything except limiting for gain!)

My only hard fast "rule” is that if you plan to have your mix mastered, don’t limit your mix at the master bus for the sake of increasing gain. Just make sure that the highest peaks are below 0dBFS. Placing a limiter at the end of your mix to catch the occasional peak is fine, in my view. Apart from that, there is no reason to avoid master mix bus processing if you like how it changes your mix. If you are using it to solve a problem, consider digging deeper or sharing what you’ve done with the mastering engineer in case there is a better option.


Happy Mixing :)!