Whenever your mix is complete, you’ll probably have to deliver stems to your client.  Stems (stereo masters) are continuous audio files that contain your full recorded mix, as well as separate audio files that add up to your full mix when played together.  As the world marches towards tapeless workflows this is starting to become the primary form of deliverable.  So here are a few pointers on printing mix stems internally within your mix session in a clean, reliable way.

Once you’ve finished your mix you want an easy means of handing it off to your client.  They need something simple that can be matched back to picture and then played on air or in the theater.  The easiest possible thing to provide is a stereo .WAV file of your mix that can by synched to picture via timecode, a 2-pop, or as an AAF import.  Often the client also wants things separated out into dialog-only, music-only, and effects-only (or possibly even small sub-groups such as ADR-only or Foley-only).  This gives them flexibility in the promo department when editing commercials, as well as future flexibility for all sorts of other distribution needs such as blu-ray, online streaming, and the like.

The solution is to print stems.  The term stem is an abbreviation for “stereo master,” which of course is a bit of a misnomer these days in the world of 5.1 surround.  The two main categories of stem are “composite” stems and “split” stems.  A composite stem consists of your full mix in a single continuous stereo or 5.1 .WAV file (or a corresponding group of mono .WAV files).  A split stem is the same thing, but contains only a single element type such as dialog-only or music-only.  Typically when all the split stems are played together they add up to the composite stem.

Once these continuos .WAV files have been created they can be matched back to picture in Avid Media Composer or Final Cut Pro simply by spotting them to their appropriate starting timecode and confirming that the 2-pop matches.  Alternatively we can export the tracks containing the stems from Pro Tools to an AAF that can be imported into the Avid, and this maintains their timeline position.

So how are stems created in the first place? They can be recorded externally on a separate Pro Tools rig, dedicated recording hardware, direct to a tape deck, or to another DAW platform.  But the easiest and most cost-effective answer is to record them internally to additional audio tracks that you create in your mix session. Let’s look at that option.

First, get the list of required stems from your client.  Here’s an example of a basic stems configuration for a stereo mix:

– Stereo Comp Mix Stem
– Stereo Dialog-only Stem
– Stereo SFX-only Stem
– Stereo Music-only Stem

Next, create corresponding audio tracks in your mix session that match the stems requirement.  These will be the tracks that you record your stems onto.

Then go to the I/O under the setup menu, go to the bus tab, and create one bus for each track.

Set the input of each of your stem tracks to its matching bus.  Set the output of each split stem track (DX, FX, MX) to the “Comp Stem Print” bus.   This means that your composite mix stem will be exactly that; a composite of the split stems.  Then send the output of the Comp Stem track to a hardware output that you can monitor from, but which is separate from your main monitor output.  In other words, if you listen to your main mix via output A1-2, set the Comp Mix Stem track output to A3-4 and set up a second set of speakers or a set of headphones on that output.  

Now comes the tricky part; you need to get your mix to the stem tracks in the first place so that you have something to record!  This part depends on a properly configured mix session, and is unique to each mixer’s session setup.  The core idea is that you need to route your Dialog Master Aux track to the Dialog Stem, your Music Master Aux track to the music stem, and so-on.  Simply add a send on each one of those aux tracks that goes to the correct bus.

Assuming this has been correctly achieved, you’re now ready to record (print) your stems internally.  Simply record-arm your stem tracks and record the full duration of your mix onto them.  If the routing is correct, the mix that you hear from output A1-2 should exactly match what you hear from output A3-4 (the Comp Mix Stem output).  I recommend recording in Punch Record mode so you can stop at any time to make fixes and then just pick up the stems recording where you left off by punching in.

The last steps after recording your stems will be to add tones and 2-pops and then consolidate the stems.  Make a selection on your stems tracks from 00:58:30:00 to 00:59:30:00, then bring up the Signal Generator AudioSuite plugin and hit Process.  Its default settings of 1kHz sine wave tone at -20dB is an industry standard for tone beds.

Repeat these steps at 00:59:58:00 for a duration of just 1 frame to create the 2-pop.  Lastly, select the entire duration of your stems tracks (starting at 00:58:30:00 and going until the end of program) and consolidate everything by hitting option+shift+3.  You’ve now created mix stems!  Just export these newly created continuous audio files and deliver them to your client.

Those are the basics of printing stems internally.