Creating and preparing stems for archival, mixing or mastering
By Rob Stewart - JustMastering.com - Last updated August 7, 2017
What are Mix stems?
What is stem mixing? What is stem mastering?
Bottom line:
- Stems are great for archiving mix projects or facilitating working with a professional mix engineer
- Stems offer a form of insurance or flexibility during mastering but they are not required.
- There is a difference between stem mixing and stem mastering
Stem mixes are the rendered versions of submixes of different groupings of tracks in your mix. For example, a "Rhythm" stem mix might be a stereo mix file of just the drums and bass. Stems usually contain all the track processing, such as reverb, or dynamic range compression, for each of the elements in the stem.
Why use Mix stems? What are stems used for?
Stems are useful for a few reasons. Stems are used in audio mastering to save time and cost for the client. Having stem mixes can save having to ask the mix engineer to make small changes to the mix, therefore saving on time or production costs. For example, a common issue is that the vocal might be slightly quiet, relative to the mix. If stems are provided, it is easy to address that without having to ask the mix engineer to make any changes to their mix. Mastering from stem mixes is a more complex and time consuming process, however, the added flexibility that comes along with it often times makes the investment well worth it.
Stems are useful if you plan to have a professional mix engineer finish your mix. By taking the time to carefully edit your recordings, and assemble a set of stems, you can save yourself a great deal of cost by allowing the mix engineer to work from a smaller set of stems.
Stems are also very useful for mix archival purposes. If you are mix engineer, and you have come to the end of a large mixing project, you could create stems for your archives so that if you had to revisit the mix years later, you would not have to re-open the full mix project and re-assemble your effects chains and any other configuration you used for the mix. By having a set of stem mixes to work from, that include all of the original processing, you are allowing yourself a great deal of flexibility. The other benefit is that by creating stem mix files, your archive files can be opened and reassembled in any DAW in the future (and we all know how quickly things change!).
What is the difference between stem mixing and stem mastering?
Stem mixing infers that you are looking for a lower cost audio mixing option. Sending a full set of tracks to a mix engineer that have not been cleaned/edited would require a significant investment, so by sending the engineer a smaller set of stems, you can save a great deal of cost. The more stems you provide, the more control the mix engineer will have over the quality of your mix.
The mix engineer will create a full mix using your stems, and will apply whatever effects processes to each stem, based on their own view of what will work best for the song. The mix engineer may or may not apply buss processing as well, but the end product is typically not a "mastered" mix, it is a stereo "mixdown" from the stems you provide. Some mix engineers will even edit your stems to a degree, for example, muting certain sections if they feel it would benefit the song.
Stem mastering is often mistaken for stem mixing. Just like with stereo audio mastering, stem mastering is much more subtle than stem mixing. It is more of a quality assurance process, where level adjustments between stems are only made for quality reasons (e.g. the vocal is sitting slightly low relative to the rest of the mix). A mastering engineer typically will not make obvious processing adjustments (dramatic EQ adjustments, heavy distortion or obvious reverb, chorus or other effects) because that is essentially a mixing task rather than a quality assurance task.
Just like with any industry, it is best to leave certain tasks to the best individual. It makes the most sense to approach a mix engineer for stem mixing services, and a mastering engineer for stem mastering.
How to create stem mix files
- Determine your purpose, first (Stem Mixing, Stem Mastering or Mix Archival?)
- Ask your contact (mix engineer, or mastering engineer) if they have any special requirements (file format for example).
- Decide how you want to split your mix into stems depending on your purpose (see "Additional Considerations" section, below, for two suggested approaches for music mastering and stem mixing).
- Remove all buss processing from the master buss (or at least any that alter dynamics such as compression and limiting).
- Solo the tracks that you wish to include in your first stem.
- Export those solo'd tracks to an audio file.
- Unsolo the tracks you just exported, and then repeat steps 3 & 4 until you have created stems for your whole mix.
Important Note: Always export your stem mixes from the exact same starting position or sample. This is important to ensure that when they are put back together, all of the stem mixes are in sync with each other.
Additional Considerations
When creating stem mixes for stem mixing or audio mastering, consider one of these two approaches.
"Gang of four" approach (recommended for Audio Mastering)
If you are preparing stems for audio mastering, I recommend this "Gang of four" approach, suggested by top audio Mastering Engineer Bob Katz. This approach allows for significant flexibility where it is needed, without adding too much to mastering costs or overriding other mix decisions made by the producer or mix engineer.
Create four mix stems, as follows:
- Stem Mix #1 - All instruments and background vocals
- Stem Mix #2 - Lead Vocal(s)
- Stem Mix #3 - Full Mix (not really a stem - this is the full mix file that can be used by the mastering engineer as a reference point)
- Stem Mix #4 - Instrumental (same as #1 without the background vocals)
This method offers plenty of flexibility for audio mastering purposes. For example, if the background vocals are too loud, that can be remedied by blending Stem Mix #4 with Stem Mix #1. Better still it allows for ultimate flexibility with the most important mix element (the lead vocal), without overriding every other mix decision made by the mix engineer/producer.
Submit discrete Mix stems (recommended for Stem Mixing or Mix Archival)
Create discrete stems for the biggest areas of concern in your mix, and leave everything else on another stem. Here is a 6-stem configuration as an example:
- Stem Mix #1 - Kick
- Stem Mix #2 - Snare
- Stem Mix #3 - Rest of the Drum kit
- Stem Mix #4 - Bass
- Stem Mix $5 - Electric Guitars
- Stem Mix #6 - Acoustic Guitars
- Stem Mix #7 - Piano
- Stem Mix #8 - Rest of the Keyboards or Strings/Brass
- Stem Mix #9 - Lead Vocal
- Stem Mix #10 - Background Vocals
- Stem Mix #11 - Everything other instrument
- Stem Mix #12 - Key effects (e.g. if you used your favorite reverb processor on the vocal, this stem could be a track of just that reverb return)
This discrete stems approach provides the mix engineer with the ultimate flexibility. It allows you and the mix engineer to further fine tune the tone and balance of the priority instruments during the mix session, while helping to keep mixing and production costs a little lower. I suggest submitting less stems to the mix engineer first. They may suggest additional stems later, if they feel it will help the song, but generally less stems will mean less complexity which will help keep costs in check.
