.ADVANCED MASTERING TECHNIQUES


Mastering benefits from the digital audio workstation. The powerful Digital Audio Workstation (DAW) lets you make edits, smooth fades, emphasize or de-emphasize the loudness of sections. A client brought a DAT with 10 songs. On one of the songs, the bass was not mixed loudly enough (this can happen to even the best producer). We were able to bring up the bass with a narrow-band equalizer that had little effect on the vocal. But when the producer took the ref home, he was dissatisfied. "You've done a wonderful job on the bass, but the delicacy of the vocal is affected too much for my goals. Do you think I can bring you a DAT of the bass part so we can raise it there? I can't possibly duplicate this mix." I told him we could handle that, asking for a DAT with a full mix reference on one channel, and the isolated bass on the other. I was able to load the DAT into my workstation, synchronize the isolated bass, and raise the bass in the mastering environment, without affecting the vocal. It was an unequivocal success. Another client doing the album of a "new age pianist" brought a four-track Exabyte archive in our workstation's format. Tracks 1 & 2 contained the full mix minus the piano, and tracks 3 & 4 contained only the piano. If all four tracks were mixed at unity gain we would end up with the full mix, but if necessary, we could level, compress, or equalize the piano separately in the mastering.


Alternate Mixes

Another approach is to ask the client to send separate "vocal up", "vocal correct", and "vocal down" mixes because the mastering I environment is ideal for making those decisions, and mastering processing may affect that delicate balance. But often it's a luxury to make separate mixes, and we dream of ways of tweaking the mix on an existing two-track. A recent client had a mixed in a bass-light room and his bass was very boomy, right up to about 180 Hz. The vocal came down slightly when I corrected the boomy bass, but through special M-S processing techniques, I was able to produce a perfectly-balanced master...which leads us to...


MS Mastering Techniques

Prior to the advent of digital processors like the Finalizer, mastering engineers were fairly limited in what we could accomplish; today, we still tell a few clients to "go back and fix it in the mix", but we have tricks up our sleeves that can accomplish wonders with a two-track mix. One ancient technique is incredibly powerful - MS Mastering.
MS stands for "Mid-Side", or "Mono-Stereo". In MS microphone technique, a cardioid, front-facing microphone is fed to the M, or mono channel, and a figure 8, side-facing microphone is fed to the S, or stereo channel. A simple decoder (just an audio mixer) combines these two channels to produce L(Left) and R(Right) outputs. Here's the decoder formula: M plus S equals L, M minus S equals R. Here's how to decode in the mixer: feed M to fader 1, S to fader 2, pan both to the left. Feed M to fader 3, S to fader 4, invert the polarity of fader 4 ("minus S"), pan both to the right. The more M in the mix, the more monophonic (centered) the material, the more S, the more wide-spread, or diffuse the material. If you mute the M channel, you will hear out of phase sound, containing largely the reverberation and the instruments at the extreme sides. Mute the S channel, and you will largely hear the vocalist; the sound collapses, missing richness and space.

There's not perfect separation between M and S channels, but enough to accomplish a lot of control on a simple 2-track. It's great for film work - the apparent distance and position of an actor can be changed by simple manipulation of two faders. M-S technique doesn't have to be reserved to a specialized miking technique. By using MS, we can separate an ordinary stereo recording into its center and side elements, and then separately process those elements. I tell my clients I'm making three tracks from two.


Do you try to identify the frequency every time you hear system feedback?


The MS adventure begins

MS is another tool that reduces compromises and increases the possibilities of mastering. The possibilities are only limited by your imagination. The Finalizer, and especially the Finalizer 96K, allows you to manipulate stereo separation using MS technique. Let's take a stereo recording with a weak, center-channel vocalist. First we put in our MS encoder, which separates the signal into M and S. Then we decrease the S level or increase the M level. We then decode that signal back into L and R. Presto, the vocal level comes up, as does the bass (usually) and every other center instrument. In addition, the stereo width narrows, which often isn't desirable. But at least we raised the vocalist and saved the day! The Finalizer's built-in width control I does this job by changing the ratio of M to S.

But we can accomplish a lot more, often with no audible compromise to the presentation, and make clients very happy. Let's take our stereo recording, encode it into MS, and apply separate equalization to the M and S channels. Here's the traditional (pre-Finalizer) method: Feed the output of the MS encoder to a dual-channel equalizer. Channel one of the equalizer contains the M channel, which has most of the vocal. Channel two contains the S channel, which has most of the ambience and side instruments. With the M channel EQ, we can raise the vocal slightly by raising (for example) the 250 Hz range, and perhaps also the presence range (5 kHz, for example). This brings up the
center vocal with little effect on the other instruments, and lowers the stereo separation almost imperceptibly. The Finalizer 96K's Spectral Stereo Imager can also "remix" this material, with a slightly different user interface. By raising the M level (reducing the width) of the 250 Hz and/or 5 Hz range, we bring up the center vocal very similarly to the traditional method, and without seriously deteriorating the imaging of the other instruments. In addition to this "remix" facility, the spectral stereo imager has very creative width control, limited only by your imagination. Spread the cymbals without losing the focus of the snare, tighten the bass image without losing stereo separation of other instruments, and so on.


Even More Advanced M-S Technique

Currently the Finalizer has a single threshold for both channels, but other TC Electronics products can accomplish even more sophisticated M-S mastering. You've all heard the mix that sounds great, but the vocal is sometimes a bit buried when the instruments get loud. We try compressing the overall mix, or even narrow band compression of the vocal range, but it worsens the great sound of the instruments. MS compression can help us isolate the compression to the center chanel.... By only compressing the M channel, we delicately bring up the center channel level when signals get loud. Or, better yet, use multiband MS compression, so, the bass (for example) is unaffected by our
compression. In other words, compress only the midrange frequencies of only the M channel... A very selective and powerful process, only available in today's digital world.


Make an UnFinalized Safety

Now you have a master, ready to send to the plant. The most professional mastering engineers make unprocessed safety copies of the music for future release on high-resolution media. If you're creating a submaster to take to a mastering house, also make an unprocessed version, as the mastering house may have a different idea of how to make your music shine.


IF YOU ANSWERED YES TO MOST OF THE QUESTIONS IN THIS TUTORIAL, THEN YOU'LL MAKE A GREAT MASTERING ENGINEER.


Quelle: Bob Katz