Mastering vs Stem Mastering: What's the Difference?
In recent years, stem mastering has skyrocketed in popularity. Unless you’re signed to a label, it isn’t always viable to hire someone to do a full mix and master for every production. Stem mastering has become an attractive option for producers working from home studios as it yields more impressive results than a stereo master but without the higher price of a full mix.
In this blog, we’ll explore the differences between traditional mastering and stem mastering to help you determine which method is best for your track.
The Role of the Mastering Engineer
The role of the mastering engineer has changed a lot over the years. Originally, they were only responsible for transferring recordings from analog tape to vinyl molds used for reproduction.
It wasn’t until 1954 when the Recording Industry Association of America introduced the RIAA equalization curve when mastering engineers started applying EQ to songs to ensure they met the new standard for vinyl records.
Mastering engineers traditionally work with a stereo mix, adjusting the frequency response, dynamics, LUFS levels, stereo imaging, and more to optimize tracks for distribution—whether you release your music on vinyl, CD, streaming services, or even eight-track cassettes.
As home studios became the primary hub for music creation and artists began to produce, record and mix their own tracks, there grew a need for a service somewhere between mixing and mastering. That’s where stem mastering comes in.
What Is Stem Mastering?
Unlike traditional mastering, in which the mastering engineer enhances a stereo file for commercial release, stem mastering combines multiple “stems” or stereo groups of instruments to create a final master.
Not to be confused with mixing, which combines all the individual channels of a project to create a stereo mix, stem mastering sessions typically include anywhere from two to eight stereo stems.
Each stem is sort of like a mini-mix of a small group of similar-sounding instruments. A simple stem mastering session may only have “vocal” and “music” stems—a common setup for hip-hop tracks. While others may have separate stereo prints for almost every group of instruments.
A more complex stem mastering session might include separate stems for kick, snare, percussion, bass, guitars, keyboards, lead vocals, and more. Each stem should be printed with all effects processing, including EQ, compression, and even time-based effects like reverb or delay. Any processing on the master channel should be bypassed when exporting stems for mastering.
By separating the stereo mix into separate instrument groups, stem mastering offers more control over your sound than traditional stereo mastering and allows mastering engineers to make more precise changes.
What’s the Difference Between Mastering and Stem Mastering?
Even though the stereo mastering process uses one stereo file and stem mastering uses multiple instrument groups, the end goal is still the same: to enhance the song and prepare it for distribution. However, each approach has pros and cons, which makes them better suited for certain tasks.
Traditional stereo mastering is a great option when you need to quickly and affordably prepare your track for distribution. Some mastering engineers are able to turn around projects with same-day service, making this a solid choice when you pushed production past your deadline.
Stereo mastering is also a good option if you’re 95% happy with the sound of the mix and you’re not looking for any significant sonic improvements from mastering.
Stem mastering is also a solid choice if you’re struggling to nail the mix. If you feel that the mix is close but something is still off and you can’t quite put your finger on it, stem mastering gives the engineer the flexibility to easily correct balance issues and adjust certain instruments without affecting the rest of the track.
For example, if the kick and the bass aren’t working well together in the mix, there’s not much you can do to fix them with a single stereo mixdown. If you boost the low-mids of a stereo mix to increase the punch of the kick, you’ll inevitably affect any other channel with frequencies in that range (vocals, piano, bass, etc).
With stem mastering, you can freely adjust the relationship between the kick and bass channels without affecting the low-end of every other track in the mix.
And since the mixer or producer took the time to balance and print stems, the mastering engineer doesn’t have to be bothered with polishing up each individual track—they can quickly tweak the sound of all the kick or bass channels at once.
Of course, the amount of control the mastering engineer has is directly related to the number of stems, and the number of channels within each stem. The more stems you create, the more control the mastering engineer has. Too many channels per stem makes it difficult to correct balance or tonal issues with the stem itself.
That’s not to say that you can’t accomplish the same end results with traditional stereo mastering—but it’s often at the expense of something else in the mix.
When To Use Stem Mastering
Not every track will need stem mastering. If you have a relatively simple track, or if you’re up against a tight deadline and need a quick turnaround, it might be safer to go with stereo mastering.
Traditional stereo mastering is also great for those releasing full-length albums or EPs and need someone to sequence the songs and ensure that each track sounds cohesive and consistent. But if you’re releasing a single and you’re not completely in love with the mix, stem mastering is the way to go. It allows the mastering engineer to fine-tune your mix with greater detail.
It’s important to note that stem mastering should not be used to make up for a bad mix. You should put the same amount of effort and focus into the level balance, EQ, dynamics, stereo width, depth and musicality of your stems that you would with your stereo mix.
The mixes that will benefit most from stem mastering will already sound very good—they just need that little bit of care and attention to detail that stereo mastering can’t provide.