Stem Files Explained

Posted by Aaron Davison on Saturday, October 27, 2012 Under: October 2012
Today's post is a guest post from producer Gary Gray.  Gary and I are hosting an upcoming 30 day long interactive workshop on music production and music licensing that starts November 1st.  This new program features one on one coaching with both Gary and myself, 30 daily tutorials on both music production and how to license your music, 30 daily licensing leads, the programs "The A To Z Of Music Licensing" And "How To Produce Music That Will Get Licensen And Make You Money" and more.  

Get all the details here:

Here's Gary:

In the new age of International Musical Collaboration on the Internet, there is a very important item that has become a new Technical “Currency” of The Indie Music Industry:  Stem Files.  I’ve noticed over the last three months, while Mentoring many students from around the world on the course “How To Produce Music That Will Get Licensed And Make You Money,” that the technology of Stem Files, a vital link between collaborators , producers, engineers and mastering engineers, is not universally understood.

Definition of a Stem File: A Stereo Digital Audio File, normally a wav file or broadcast wav file (A broadcast wav file is a wav file format with the addition of metadata to facilitate the seamless exchange of sound data between different computer platforms and applications; used quite often in film, television and commercial projects) which contains A GROUP OF instruments or vocal tracks (A SUBMIX) in an unedited, consolidated, single file. This Stem File, sometimes called a Submix File, along with the other Stem Files of a project -- each containing a group of instruments or vocal tracks -- all START AT ZERO EXACTLY.  This means that the left edge of any Stem File starts exactly where the left edge of all Stem Files starts; which we arbitrarily call ZERO.  Note that the Stem Files must all start EXACTLY at the same spot. The Stem Files may or may not end at the exact same spot, but they must, to be acceptable Stem Files BEGIN at the EXACT same spot. The reason for exact alignment is PHASING and PHASE PROBLEMS that can develop if one or more Stem Files are not in exact alignment.  If the Stem Files do not each begin at the exact same spot, the Collaborator or Mastering Engineer who is receiving these files will be forced to try and align the tracks manually.  What is not generally known is that the most minutely small (microseconds) of misalignment can adversely affect the mixing and mastering process in a HUGE way.  (The next time you decide to slide a track to the left or right even slightly, be sure to listen to your mix in MONO – and if there is a phase problem, you will notice that the track you slid over will sound weaker, with less low end and less punch.

What are Stem Files Used For?

Stem Files are used for collaboration with other producers and engineers; specifically for re-mixing and mastering.  Instead of mixing every single instrument and vocal track, with Stem Files you are mixing sub-groups or sub-mixes.  

For mastering; instead of mastering one stereo file, the mastering engineer can master each Stem File (sub-group), and the overall song itself, allowing him to actually mix during the process of mastering.  For instance, if you sent the mastering engineer just the typical stereo mix file, he might find that the vocals are too buried in the mix and he may try, with mastering techniques, to bring out the vocals more.  While doing so, he may find that he made the vocals sound much better, but now the guitars are sounding terrible.  So, the trend among many mastering engineers over the last several years is that they will ask the engineer who sent the mix to separate the track into Stem Files (sub-groups), so that he can make adjustments to specific areas of the mix (vocals in this case) without adversely affecting other areas of the mix (guitars in this case).

Here’s a typical example:  You start your mixing process with 30 tracks – 8 tracks of drums, 1 track of bass, 5 tracks of guitars 5 tracks of keyboards, 3 tracks of strings, 2 tracks of lead vocals and 6 tracks of background vocals.  To create Stem Files there is no rule or absolute way that you have to group your tracks together.  For instance you could bounce all of your 8 separate drum tracks into one stereo file.  That would be your Drums Stem File.  You could bounce all of your guitar tracks into one stereo file.  That would be your Guitars Stem File, etc. 

However, in order to give your collaborator or your mastering engineer more control of the project and increase the quality of your final product, you could take this approach:

Kick Drum Track

Snare Drum Track

All Other Drums Track

Bass Track

Rhythm Guitars Track

Lead Guitars Track

Keyboards Track

Background Vocals Track

Lead Vocals Track

Strings Track

The example above would give any collaborator doing a re-mix, or any mastering engineer, complete freedom and control to do the very best they could do to create a high quality production. Note that even though the Kick, Snare and Bass tracks are single instruments, these files are still considered Stem Files because they are being used with other Stem Files for the purpose of a re-mix or Stem Mastering.

Here’s another real-life example:

Let’s say we use the example above where the Mastering Engineer found that the vocals were buried too far into the mix.  But he really likes the instruments and how they are mixed. He might ask for a very simple separation of Stem Files; namely two:

All Vocals Track

All Instruments Track

The example above is very common.  It also serves another purpose: it gives the mastering engineer the ability to master two versions of your song:  One with vocals and one instrumental version, which is key for getting licensing deals.  Note: Even if your Mastering Engineer does not ask for Stem Files, make sure and send him an instrumental version of your song to Master, along with the full version with vocals.  And if YOU are the Mastering Engineer (which I wholeheartedly encourage!)  than all of this information on Stem Files still applies to yourself.

What about Bit Rate and Bit Depth?  Should I bounce my Stem Files at 48 kHz, 24 bit? 44.1 kHz 16 bit? 96 kHz 24 bit??? Is there an optimum Bit Rate and Bit Depth I should use???

To gain a very clear, concise and full understanding of the difference between Bit Rate and Bit Depth, go to and see the video at the bottom of the home page.

Bit Rate is expressed in this way: 96 kHz or 48 kHz or 44.1 kHz.

Bit Depth is expressed in this way:  24 bit or 16 bit.

If you are sending your files to a Mastering Engineer – ask the Mastering Engineer what Bit Rate and Bit Depth they prefer.  If the Mastering Engineer says “it doesn’t matter” or if they do not specify, then the best rule of thumb is this:   Bounce your Stem Files with the same Bit Rate and Bit Depth that the project was recorded at.  Any good Mastering Engineer can get an excellent final master with files that are at least 44.1 kHz 16 bit.   There are tons of articles written on this subject and I can tell you after thousands of hours of mixing and mastering that an empirical truth emerges above the din of “experts:”   An engineer with good ears, decent equipment and ample experience can create a masterpiece recording with a Bit Rate or Bit Depth of 44.1 kHz 16 Bit or above.  And that includes Major Film Score sound tracks.  There is ONE exception:  If you are planning on ending up with a Surround Sound Mix – because of the current state of technology, it is best to record, mix and master at 96 Khz, 24 Bit.  But even then, don’t worry if a Major Motion Picture Music Supervisor picks up one of your tracks for a Licensing Deal for a Surround Sound Master and you recorded it at 44.1 kHz 16 Bit – it CAN be converted safely.

To learn more about how to create Stem Files, how to master and how to improve your music productions in general, sign up for the new 30 Day Music Licensing And Production workshop starting Nov 1! This 30 day long program focuses on both how to produce tracks that meet the standards for music licensing and how to license music in film and television.  The workshop features private coaching with me and Aaron Davison, 30 daily tutorials on both music production and music licensing, thirty daily licensing leads and much more. The program is very reasonably priced, but there are limited slots.

Get all the details here:

In : October 2012 

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