Separation Anxiety

Mastering engineer JOHN VESTMAN and DON SUNDSTROM manage to make your mastering obsolete. And you’ll thank them for it
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Every engineer has experienced it: The mix sounds really good . . . it’s 3:00 am and the mix has to be done tonight . . . but should the vocal be nudged up a tad, or is it just right? Are the drums loud enough, or are the guitars too loud? Producers, artists, labels and engineers want that “edge” — yet increasing DAW technology doesn’t always guarantee a perfect mix. So engineers cut, boost, clone and scramble to achieve their best — and then they leave the final sonic refinements to the mastering facility.

With traditional techniques, an expert mastering engineer can enhance certain elements in your mix — up to a point. A two-track mix has all the musical components embedded together, so too many alterations to one area may cause problems somewhere else. Therefore, the mastering engineer must always be aware of how many alterations work, and when “less is more.”

In response to the needs of a more diverse professional market, an expanded mastering process is defined by veteran mastering engineer John Vestman and engineer Don Sundstrom. Calling it “separation mastering,” Vestman’s claim that it gives better sound, fuller detail and spatiality, while allowing more control over major musical elements of the final product — if even half true — could healthily add that extra edge to any project that needs that extra edge. Translation: all of them.


“After mixing a standard 2-Track master, the mix engineer simply records stereo tracks of groups of separated instruments and vocals,” says Vestman. “A common set of stereo separations would include (1) all drums (2) bass (3) all remaining instruments and (4) all vocals. The Separations are brought in and recombined in the mastering room’s source DAW, along with the stereo mix for reference. This makes for a dramatic increase in sonic control because the mastering engineer can process certain frequencies on one separation without imposing on the sound of the other musical elements.

This is ideal when a vocal needs to be treated differently than the drums, or the guitars need to be enhanced in ways that wouldn’t benefit the vocals, etc. The mastering engineer’s hands are no longer tied by traditional compromises. Plus the very nature of the mastering studio’s tailored, acoustic environment and the engineer’s ‘golden’ experience sets up the ideal context for this first-up delivery format. More good news: Most DAW owners are already set up (at no cost) to make separations with almost no learning curve.”


“Stems (or subgroups) are used in many different ways, and may or may not have reverbs or effects embedded directly in them. Separations always contain the reverbs and effects that belong to the respective tracks being grouped. Engineers may also use 10 to 20 sets of stems while mixing, but generally four to eight stereo sets of separations are ideal to deliver for mastering. Many mastering studios currently hesitate to accept stems because they know that there can be time-consuming variables, whereas the Separation Mastering format is a clear, efficient first-up method to achieve superior sound right now.

Like the concept of color separations in the world of print, separation mastering makes total sense to engineers and artists who struggle committing to 2-tracks. Yet the artist’s approved stereo mix is a key component of separation mastering. The stereo mix is loaded in and available to A-B compare so that the artist’s original intent is always honored. A-B listening is an important aspect of the mastering process.

Can this process really deliver better sound while making your final mixing process easier? Yeah, particularly since it’s non-destructive and recallable, it takes pressure off the mixing engineer who’s running out of time (or budget), and it eliminates the need for alternate “up/down” versions. Up until now, why have so many studios stuck to the limitations of 2-track masters? Because that’s just the way it’s historically been done — for about 50 years.”


“Starting in the late 1950s, mixes headed for stereo vinyl records were ‘mastered’ by transferring the signal of the 2-track master tape into a 2-channel electro-mechanical lathe. The lathe physically cut grooves into a lacquer-coated master disc (hence the phrase ‘cutting a record’). Through the 1960s and ’70s, regardless of the number of tracks available in the studio, a mixdown would occur to a 2-track master tape that would feed a 2-track lathe. CDs replaced lathes in the ’80s but the 2-track feed tradition continued. When big studios went to digital formats instead of tape, the 2-track tradition continued on. Why? Because it still worked, and there was no problem to address.

Back then, mixes brought in to mastering were generally consistent and sonically well balanced. But gradually, affordable multitrack equipment started empowering a new generation to record and mix outside the large studios, presenting mastering engineers with new sonic balance challenges. However, these increasing mix variations were manageable with new digital technology processors, so the 2-track final mix lived on. But the sun was setting.

However, the recent DAW revolution completely altered the recording landscape forever, and decentralized where great recordings had to be made. Everyone now is mixing music. But why isn’t making a good mix getting easier? Certainly the drive for hotter and hotter CD levels have made it so more sound is getting packed into a smaller dynamic space — so it’s common to find many recordists flooding Internet forums to find their answers.

You see, good mixing and good mastering is not just about plug-ins. The aspect of technology must balance with an accurate monitoring environment and engineering skill/experience. Out of these three aspects, the technology can be strong but the other aspects equally effect the overall sound of the mix. When a mix is locked down to 2-tracks, mastering engineers can correct some mix imbalances with surgical EQ and other high-end signal processing (such as multi-band processors that can isolate specific frequency areas). But altering major elements embedded together in a stereo mix can compromise the sound of other overlapping elements (e.g., de-essing a vocal starts dulling the cymbals or snare).

Making separations, though, takes a very small amount of time for the benefit it offers. In the mix room, the engineer simply ‘separates’ the final mix into a small number of major element or element groups. These are bounced down separately (e.g., vocals, bass, drums, remaining instruments) and the files include every track and track FX in the recording.

While it may seem like just a deceptively simple bounce procedure change, the sonic power this unleashes is significant. Session experience demonstrates that projects mastered with separations have more width and depth, better musical articulation, and more natural transients. The format opens the sound more than the same material mastered from their conventional 2-track mix. It offers more flexibility when artists and/or label A&R want a competitive sound and last-minute changes. Using separations also lets the mastering engineer restore the relative punch of the drums when louder, squashed-hot CD levels are desired.


“Separation Mastering is a pretty flexible standardized handshake protocol between the recording studio DAW and the mastering studio’s source DAW. It also provides a good base for future remixes, (e.g., film, video game, porta-pod, and so on) and maintaining recallable backups. It eases the creation of mastered TV mixes and instrumental tracks and eliminates the need for alternate mixes.

But separation mastering is NOT remixing anymore than ‘surgical’ EQ, or fine-tooth multi-band processing would be considered re-mixing. The separations format is good as the first up, preferred method of submitting a project to mastering, particularly since the approved 2-track stereo mix is included in the format (and can always be used in cases where the producer prefers a more compressed-in stereo sound field).”

Can, however, is different from will, or has.

Multiple Grammy-winning engineer Erik Zobler (George Duke, Anita Baker) concludes with a fitting coda, “Separation mastering makes a lot of sense in today’s music scene. Many people are mixing their own music and are not relying on a professional mixing engineer’s ears. Separation mastering lets the mastering engineer accurately rebalance aspects of a mix if necessary. Artists and producers shouldn’t be afraid of separation mastering, since mastering is a non-destructive process. In the hands of a competent mastering engineer, it delivers much better results than the typical 2-channel mastering process.”

And according to Vestman, discussions with DAW software companies about incorporating separation features have centered on adapting existing multi-channel surround mix busses for “dual use” by including a “stereo” configuration for assigning and automatically creating multiple separation files and integrating stereo buss processors.

Well, at least they’re talking.