Stem Mastering for Enhanced Audio Quality

Stem mastering is a relatively recent development in the world of audio engineering. It’s a process that can have a pretty dramatic effect on the final result of a musical production, but what is it and how does it differ from traditional stereo mastering? That’s what we are going to dive into.

Traditional Stereo Mastering

In a traditional mastering scenario, you are given stereo files. No matter how many tracks make up the mix of a song, it is mixed down to a single stereo track. Within the confines of these stereo files, the mastering engineer works to correct any issues and increase the fidelity of the audio being processed. Typically, the goal isn’t to rebalance the mix, just make corrections and enhance an already balanced mix.

There are quite a few limitations with stereo mastering since you are dealing with a mix that has multiple elements spread across the entire frequency space. These limitations aren’t usually problematic assuming a well-balanced mix, but let’s take a look at a scenario.

You have a mix where the vocals are too bright but the instrumental portion that makes up the music is dull. You want to brighten up the instrumental but doing that would make the vocals which were too bright to begin with, insanely bright. Sure, you can try and resort to some creative processing to compensate for this, but it is less than ideal. Neither the instrumental nor the vocals are going to be where they need to be and that’s the tradeoff. This is just one of many potential scenarios that happen with increasing regularity.

In the previous case, you go back to the mixer/artist/producer and ask for a revision explaining the situation. Hopefully, on the next run, you get what you need to finish the master.

Stem Mastering

Stem mastering aims to address some of the issues that can’t be addressed by traditional stereo mastering. Instead of just having one stereo mix of the entire song, you have multiple stereo files that make up the core elements of the mix. You then take these individual stereo files and create a single stereo master from them.

These audio files provided could be as simple as an instrumental and a vocal stem to the individual subgroups of instruments that make up the mix. There are no rules here on which stems to provide and every engineer is going to have their preference, but let’s take an example of what you might provide for a modern a rock song:

  • Drums
  • Bass
  • Guitars
  • Leads
  • Synths / Pianos
  • Vocals
  • Sound Effects (Car crashes, sub drops, reverse cymbals, etc) 
  • Effects (Delays, Reverbs, etc)

This is just 8 stereo tracks. So the entire mix, which may have been 100’s of tracks is now broken down into just 8 tracks. Or maybe even fewer tracks, here is an example with 5:

  • Drums
  • Bass
  • Guitars
  • Vocals
  • (Everything Else)

Obviously, you could be more or less granular here, but you get the point. Now you can see where the mastering engineer would have more control over individual elements that make up the mix. So that overly bright vocal can be fixed without affecting the other elements that comprise the song. Same goes for countless other issues including the level of each of the stems.

Issues don’t have to be as drastic as the ones pointed out. Sometimes even well-mixed songs can benefit from a bit of additional clarity and processing on individual elements. Mix engineers typically spend more time with the material so ear fatigue and just getting accustomed to how things sound can happen.

With the stem mastering approach, you end up with material that is more punchy, clear, and balanced with fewer tradeoffs. If this mix needed a bit of help from the get-go, this can be exactly what is needed.

Why Stem Mastering

Stem mastering is a product of the modern music production environment. Mix engineers are often asked to do more with less in a shorter period. In many cases, there are also fewer people involved in the music production process. One person may have done the production, recording, editing, and mixing of the material. With fewer ears working on a project and less time available, it’s much easier for issues to creep in and persist throughout a production.

Another thing to think about is that more people are dabbling in audio engineering. Often they are working in less than optimal listening and monitoring conditions. These factors either in part or whole can allow a lot more issues to creep into the production before the mastering stage.

In all of these cases, the perspective provided by an experienced mastering engineer providing stem mastering can be invaluable.

Recently I received a mix that had some issues in the high end. It was difficult given the stereo WAV file of the mix to determine just what was causing the problems due to the wall of sound coming out of this rock track. What were the biggest offenders? Was it the cymbals? The electric guitar? A combination of both? Come to find out it was a combination of both. I wouldn’t have known exactly or have been able to correct these issues without the individual stems of the song.

But what about cases where the mix is well balanced?

Even in cases where the mix is well balanced, stem mastering can still be beneficial. After all, it is still another set of ears in another environment. The benefit here is that where there aren’t significant issues, small things can be corrected without affecting the overall balance leaving more of the mix balance intact. Stem mastering can increase that amount of clarity and loudness that is capable out of the mix.

How is Stem Mastering Different Than Mixing?

This is a good question with a cloudy and non-specific answer. The truth of the matter is that it can certainly be similar to mixing and given that the stems of a song are given to the mastering engineer, it’s very easy to rebalance the mix during mastering. The reality of the situation though is this may very well be what needs to happen.

How I look at it is the mix engineer is the one who sets up the initial balance and levels. They process the individual elements and buses of the song. Mixers get the potentially hundreds of tracks down into just a few subgroups. They also add the creative effects and set the direction of the mix along with the artist and producer. They should be free to explore their creativity.

The mastering engineer is in a different room with a different monitoring, listening environment, and perspective. The mastering engineer typically is in a more critical listening environment and taking an approach that is more clinical. Both the mixer and mastering engineer working together to create something better because it’s the sum of both their work. Teamwork, that’s what music is all about.

The mix engineer is the pitcher throwing a great pitch, and the mastering engineer is the batter hitting that great pitch out of the park. Yes, I know the pitcher and the batter are on different teams, but you get my point.

Stem Mastering Viewpoints

Some mastering engineers don’t like stem mastering. They feel that the onus of getting all of the elements balanced should be placed solely in the hands of the mix engineer. In a perfect world, this would absolutely be the case. But we all know in the world of modern audio production this just isn’t the reality we are living in. 
Personally, I’d rather help someone that needs it for their production and do the best I can for them. If they can work on something and be proud of it in the end, then I’ve done my job. 
Stem mastering can also be a good learning tool for mixers who are looking to gain experience. Hearing the result can help when applying mix decisions to future songs.


So now that I’ve made Stem Mastering sound like some sort of silver bullet, I think it would be an excellent time to point out a couple of potential downsides.

The first thing to keep in mind is that it’s certainly possible to make things worse. Things like an inexperienced engineer, sub-par room, poor monitoring, and a variety of other things can mean that the mix is even more unbalanced than it was previously. Ouch!

Stem mastering can cost slightly more than traditional mastering services. This is because there are more tracks and it takes more time for setup and completion of the master.

It should also go without saying that stem mastering cannot fix a bad recording. A poor performance or severely compromised files are something that can’t be fixed by this process.

Moral of the story is work with someone you trust and create a relationship with them.

Our Approach To Stem Mastering

We will work with you to get the necessary stems and set them up in a session making sure there are no problems with the files. We can provide insight on which stems to provide given your particular songs and genre.

We will ask that you take any dynamics processing on the master bus off (this is because the balance can change without all of the elements flowing through the master bus).

Do not adjust any faders or perform processing tasks like normalization. We want to be able to pull in your files, hit play and hear the mix pretty much as you hear it.

Just like most projects we handle each project differently based on what it called for but being a hybrid environment, there is almost always an analog component.

What you receive in the end is stereo masters for your project which you can then use for distribution just like you would in a traditional mastering scenario.


Stem mastering can be a great tool in the music production arsenal allowing the mastering engineer to make corrections and enhancements that they couldn’t do in a traditional mastering scenario. This flexibility can be beneficial for both balanced and unbalanced mixes alike.

Stem Mastering for us is a collaborative effort, we work with you to exceed expectations and provide you the best result possible.

If you have any questions about The Freq Zone’s Stem Mastering services or any services we provide, please don’t hesitate to reach out for more info {at} freqzone {dot} com

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