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What is stem mastering?
What are the pros and cons of using stem mastering over stereo mastering?
Learn how to prepare your mix for stem mastering, without driving your mastering engineer nuts.
For decades, mastering has been the final step in the music production process. The mastering engineer’s goal is to put the finishing touches on the final mix to prepare a song for distribution. This process has traditionally been done using a stereo bounce of a song’s final mix.
In recent years, however, a new technique has emerged. Some modern artists are adopting the technique of stem mastering, which gives us the ability to work with multiple instrument groups such as drums, bass, vocals, and so on.
You might be wondering what the point of stem mastering is. After all, plenty of hit songs have been made by mastering a stereo file right? However, if you are an independent musician or producer working out of a home studio, stem mastering may prove to be a viable option for you.
Why Should You Use Stem Mastering?
The biggest advantage to stem mastering is control. Allowing the mastering engineer to tweak specific instruments instead of a whole mix gives them more control over the sound of the final master. This results in a final product that has been expertly engineered to sound awesome – assuming it’s done right.
If you are working out of a home studio, giving the mastering engineer stems can help your tracks sound like they were done in a professional studio.
Stereo Mastering vs Stem Mastering
You are probably familiar with the traditional method of stereo mastering. As mentioned previously, stereo mastering is when the mastering engineer is given the final stereo mix of a song. The engineer then does any final processing that is deemed necessary to the file (EQ, compression, stereo imaging, etc.). Any processing that is done affects the entire stereo mix.
In stem mastering, “stems,” or audio files containing similar instruments grouped together are delivered to the mastering engineer. This could be as simple as sending an instrumental and vocal stem, or as complex as sending instrument group stems (i.e. a drums stem, bass stem, vocal stem, etc.).
This allows the engineer to perform any processing deemed necessary on individual instrument groups. Therefore, any processing that is done does not have to affect the entire stereo mix.
How Is Stem Mastering Different To Mixing?
The description of the stem mastering process may sound like it is just an additional mixing stage. However, it is a very different process and should not be used to try and fix a bad mix!
In this process, stems are created after the final mix is completed. The mix balance and processing on individual channels has been done, effects have been created, and mix automation has been written. The goal of stem mastering is to take individual “stems” of each instrument group and put final touches on them to create a polished final product.
If you are going to have a mastering engineer do this, take the time to get your final mix as good as you can get it before creating stems. The mastering stage can only fix so much.
Pros and Cons of Using Stem Mastering Over Stereo Mastering
Now that you understand the difference between stereo mastering and stem mastering, you might be wondering if stem mastering is right for your tracks.
The truth is that there is no right answer, but there are pros and cons to both mastering methods, and they are important to consider when making your decision.
Pro: Greater Control in the Mastering Process
As mentioned previously, stem mastering allows the mastering engineer to have a greater amount of control in the mastering process.
For example, let’s say your mastering engineer notices the lead vocals are too boomy. If the engineer only had a stereo file, there is not much they could do. A cut in the low-mid frequencies to reduce boominess would ultimately affect every other instrument in that frequency range. If the engineer has access to the stems, however, they can easily make those adjustments without affecting the rest of the elements in the mix.
This could make stem mastering a good option if you feel like you are struggling to get your mix exactly where you want it to be.
Having a fresh pair of ears on your music can be helpful when you feel stuck. Hiring an experienced mastering engineer to do this may allow minor issues in specific instrument groups to be fixed before your track gets sent to the masses.
Pro: Ability to Quickly Make Alternate Masters of Your Song
If your mastering engineer has access to the stems of your song, it is easy for them to quickly create fully mastered alternate versions of your song. You might want to have a final master to release on streaming services, but also an instrumental version for yourself or your client to sing along with in live performances (remember those?).
In the stem mastering process, your mastering engineer can easily mute the vocals in their mastering session and create that version for you.
Note that this could certainly be done in the mixing process if you are doing stereo mastering. However, you would have to make stereo files of these alternate versions and send them to the mastering engineer.
Con: Bad Mixes Will Not Be Fixed!
While the extra control in the audio mastering process may be beneficial, remember that stem mastering cannot fix a bad mix! If you struggle with mixing, I recommend you take the time to improve your skills or hire a mixing engineer before you consider stem mastering.
Remember that the goal of mastering is to take a mix that is 95%-99% there and make it 100% there. If your mix is not that close, stem mastering will not be effective in cleaning it up.
A professional mix session can easily involve more than 30 tracks in a single song. With stem mastering, you would be including multiple tracks in a single stem. So it’s just not the same!
Con: Stem Mastering Could Cost You More Time and Money
If you feel like your mix is ready for mastering, the greatest factor in your decision may be the extra time and money involved in stem mastering.
It is understandable that it takes more time to master stems than it does to master a stereo file, and so mastering engineers will charge you more for the extra time. If you are working with a mixing engineer, it will be their responsibility to create the stems, which takes extra time that they will charge you for.
If you are the mix engineer, it will personally take you extra time to create the stems. Then there is the issue of transferring the stems to the mastering engineer. You may have to pay for a premium account on a file transferring service in order to be able to transfer all your stems to the engineer.
The extra cost may not be a big deal for a single song, but it can add up if you are looking at mastering a longer project like an album. Doing stem mastering on every single track would make the mastering process longer as well, so expect to wait a while for the final masters. Add on the extra money you need to get the necessary storage in your file transferring service, and this option may end up being too costly for you.
Ultimately, you will have to consider these pros and cons and decide which option best suits you. If you cannot afford this method, remember that you can still create good masters with stereo files, you just have to rely more on good mixes for this to happen.
Tips for Delivering Stems to Your Mastering Engineer
If you’ve decided that stem mastering is right for you, here are some tips for when you are printing stems to deliver to your mastering engineer:
1. Render your stems at the sample rate and bit depth of your session.
This will ensure that the audio quality of the stems will be the same as your DAW session. No matter what DAW you are in, you can set the bit depth and sample rate of your stems before you print each audio file.
2. Make sure all your stems start and end at the same time.
No engineer likes having to organize tracks they’re not familiar with. Check that the length of each stem is identical and save yourself the frustration of trying to communicate where (for example) the vocals are supposed to go. You will thank yourself later.
The easiest way to do this is to make a timeline selection in your DAW. This ensures your files will start and end within the timeline selection.
3. Print as many stems as you think you need
There is no “correct amount” of stems to send per song.
You can send just an instrumental and vocal stem, or make stems for each instrument group. Some people create, for example, kick and bass stems in case the low-end needs to be tweaked.
This can be useful if you think a specific element of an instrument group needs processing done for the final master. The bottom line is to create stems for anything you want the mastering engineer to have control over, just don’t send them all the individual tracks! That is what mixing is for.
4. You may want to bypass any master bus processing when creating stems.
If you used any EQ, dynamics processing, etc. on your master bus, consider whether you want to leave it on or not. If you would like the engineer to have more control over the sound quality of the final master, or aren’t confident in your master bus processing, it would be best to bypass it.
In general, it’s a good idea to turn this extra processing off. These effects make sense when all the tracks are mixed together, but on the individual parts they may only make things worse.
In this case, it may be good to send the engineer a mixdown with your master bus processing on it for reference.
5. Check your stems before you send them off!!!
Take all your stems and place them in a new session. Make sure that all the stems combined with their faders at unity sound exactly like your mix. If they do not, go back and fix them before you send them to your engineer.
This step is sometimes so obvious it’s easy to miss! Mistakes happen, especially if you’re rushing to get things sent off for mastering. But slipping up here can cost time and money, so always check your work.
Other Important Considerations
Mixing Into a Limiter
If you are mixing into a limiter, you cannot print your stems with the limiter on and have the result sound exactly like your mix. The limiter is set to respond to the dynamics of the entire mix, so it will behave differently when printing individual stems. There are two solutions to this:
Bypass the limiter when printing stems. Limiting is something that is done in the mastering stage anyway, so if you’re not super attached to the sound, just bypass it.
If you like the limiting you did on the master bus, you can create a mix stem and use it to feed the side-chain input of your limiter. This will allow the limiter to react the way it does when the entire mix is played back. (If you don’t know what sidechain compression is, learn about it here.)
Briefing Your Mastering Engineer
In addition to your stems, it can be helpful to send any useful notes about your session that you have. Some important things to mention are things you do and don’t like about your mix and want changed in the mastering process (i.e. “the vocals sound too harsh,” “I want the drums to be punchier,” etc.).
These notes will help the engineer retain what you like about the mix and tweak the areas you’re concerned about. If you’re not sure what needs tweaking, that’s okay! That’s why you are giving the engineer your stems, so they can spot potential issues and fix them.
Stem mastering can provide a level of flexibility that stereo mastering cannot. It is easier to make changes to specific instruments which can result in a higher-quality track.
Ultimately you have to decide whether the extra cost and time involved in stem mastering is worth it for you. Remember, if you have a good mix, stereo mastering can still be effective. There is no right method, only the one that works for you. Happy mastering!