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Piecing Together a Great Audio Master
Written by Myles Boisen - 2006 Prism Business Media Inc. Reprinted with Permission.
Mastering and editing a recording project is analogous to assembling an art exhibit. Every piece may be great on its own; however, the pieces will have a much greater impact as a collection once they are cleaned up, properly framed, and displayed in a way that shows each in the best possible light. This kind of attention to detail makes the whole artistic experience greater than the sum of its parts.

The goal of mastering is to make the music sound good on a variety of systems and delivery media and to unify the program from beginning to end through careful quality control. Mastering a project from one studio and one set of sessions is straightforward because the masters will be on one format and the sound will be consistent from one piece to the next. Assembling compilations, on the other hand, makes interesting demands on the mastering engineer.

Compilations run the gamut, from tribute albums to holiday records to ethnic music collections, and they range in size from a single CD to multiple-disc box sets. Because each song usually comes from a different artist and a different set of recording circumstances (including location and studio recordings), it is likely that the engineer will receive a wide variety of masters on various analog and digital media.

The mastering engineer's challenge is to achieve a consistent, unified sound throughout the compilation. This is the primary focus as the engineer masters each piece and makes improvements to the mixes by using EQ and compression, changing the stereo image, and adding reverb.

Preparation
As with any phase of studio recording, the amount of preparation you do can make or break a session. This is especially true with multiple-source mastering jobs. Media compatibility is a common problem, and dealing with it can be particularly time-consuming. I have received masters on almost every imaginable format, from old reel-to-reels and cassettes to assorted digital media, and I've learned the hard way that it is essential to know ahead of time the format of each mix I will receive. That way I can have the proper machines on hand.

Before the session begins, make sure you have received documentation and noise-reduction specifications for all masters used in the project. Cue any cassettes involved ahead of time. If there will be an outside producer/ coordinator, don't assume that they know what formats the mixes are on; a little detective work may be required. Beware of the rare client who doesn't understand that he or she has to mix the multitrack masters before bringing them in for mastering. Asking the right questions well in advance of your session will avert potential disasters.

Mental and physical preparations are equally important for a demanding mastering session. There's no room for the "fix it in the mix" approach at this stage, and the quality of the finished product depends entirely on your alertness, attention to small details, and ability to make critical listening decisions for hours on end. Make sure you're rested, start your session with fresh ears and a full belly, and forget about using recreational drugs or alcohol until the computer is turned off and the final CD is burned and safely nestled in its jewel box.

Of course, your monitoring environment must be suited to mastering. It's unwise to master on speakers that don't offer basically flat frequency response, or to master in a room that hasn't been treated or tuned to eliminate major resonant modes. You aren't doing anyone a favor by mastering in an unreliable monitoring environment, and you might do irreparable damage not only to the recordings but to your reputation as well.

Transfer Logistics
When you have your room, your attitude, the necessary equipment, and the source tapes and other materials together, it's time to get to work. On a single-source mastering project (for instance, with a band that is recording an album), I usually plan on spending about six hours (approximately 10 to 12 cuts, 50 minutes total time). An hour-long compilation, done to high standards, can easily take ten hours or more.

The first half of any mastering session is generally spent listening to the source tapes, discussing various processing options with the client or producer, and making sure that he or she understands what can and cannot be done. This is the stage at which you make most of your crucial listening decisions. You should check each piece for inconsistencies and other problems; adjust it to an optimal gain setting; equalize it; convert it to 16-bit, 44.1 kHz digital format, if necessary; and import it into a 2-track editing program.

When assembling a compilation CD, you can reasonably expect to receive material in more than one media format, including a mixture of digital sources recorded at 44.1 and 48 kHz. To simplify the task of sample-rate conversion, presort your source material and transfer all the recordings with a similar format together (for example, all the 48 kHz DATs) before moving to the next format. This will not only save time but will also reduce the potential for human error, such as transferring a DAT at the wrong sampling rate.

Although any mixdown media can be used for mastering, by far the most common for compilations are digital audio tape, CD-R, and cassette. As I load tracks from analog masters into the computer, I run them through a 2-channel parametric equalizer, and from there I send them into a digital multi-effects processor for additional processing and analog-to-digital conversion.

For digital sources that are recorded at 44.1 kHz (DAT, CD, MDM, MiniDisc, or digital audio workstation), I use the 5-band digital parametric EQ and other processing functions of a TC Electronics M2000. For DAT sources recorded at 48 kHz, I either make an analog transfer through a parametric EQ or simply connect the analog outputs of a professional-quality DAT machine to the analog inputs of the M2000 using high-quality balanced cables. I have found both of these methods to be sufficient for maintaining the resolution of the original digital signal while making a sample-rate conversion in real time from 48 kHz to 44.1 kHz. Many digital editing programs can do sample-rate conversion, although this can be somewhat time-consuming on older computers.

As you enter the source material into your computer, keep a detailed log that includes source-tape information, EQ and other transfer processing, start and end times for each track, markers for editing, playlists, and any other information that might be helpful in the future to you or another engineer.

Corrective EQ
Equalization is a major part of most mastering sessions. This is a process in which an inexperienced engineer can do more harm than good. To avoid making any big mistakes at this stage, take the time to familiarize yourself with the way that professionally mastered records sound on your system. Always A/B any EQ changes for yourself and your client before you commit to them-and be conservative, especially when boosting levels. A single cut or boost of 2 dB can have a major impact on any mix, and with good equipment subtle adjustments of 0.5 dB or less are usually audible.

For the sake of continuity on a compilation, some pieces may need major sonic surgery, and this may require multiband cuts and boosts of 3 to 4 dB or more once everything is in the computer. Bear in mind that most people listen to recorded music on relatively small, inexpensive speakers (car stereos, boom boxes, bookshelf systems, and so on) at moderate volume levels, so make sure the tracks have sufficient definition at a soft listening level. Pay special attention to the extreme highest and lowest frequencies, which often get lost on consumer-grade monitors. Keep your ears fresh throughout this part of the process by limiting loud monitoring time and taking breaks as needed.

I like to deal with corrective EQ in real time during the transfer stage. I listen to a few passes of each individual piece at a moderate volume level and formulate an EQ curve to compensate for deficiencies in the recording medium, the mixing environment, or the acoustical space where the music was recorded.

For example, stereo-miked live recordings often have at least one band of pronounced, boxy room tone between 250 and 400 Hz, which can be easily detected by boosting the gain and sweeping the frequency of a medium-bandwidth filter within this range. When the EQ boost centers on this acoustical resonance mode, you will notice an audible increase of mushy midrange reverberation; gently attenuate the resonance while adjusting the frequency bandwidth as needed.

You can determine the proper amount of attenuation by comparing the EQ in its active and bypassed positions. You can also fine-tune the EQ parameters so that an acceptable increase in midrange clarity occurs with only a minimal decrease of overall warmth, instrumental tone, and other desirable low-end qualities. A skillful attenuation of the room's resonant frequencies often reduces the natural reverberation characteristics of the acoustical space, making it possible to further enhance a live recording by adding reverb while mastering. Begin with a conservative cut of 1 to 2 dB, increasing the attenuation as necessary.

You can deal with high-frequency harshness (typical of digital multitrack recordings, particularly on the original ADATs and early DAT recorders) by using a similar process, this time concentrating on the frequency range between 2 and 6 kHz. Be careful not to take too big a bite out of the highs in this range, and do a thorough A/B comparison to make sure that you aren't dulling the high frequencies or losing important detail and definition.

Broadband EQ boosting is another effective mastering tool. When applied skillfully, it can enhance the fullness and overall impact of a recording. Typical scenarios for this type of EQ processing include high-shelving boosts above 10 or 11 kHz to add shimmer and upper harmonics; low-shelving boosts below 80 to 100 Hz to enhance the power of the low drums and bass fundamentals; upper-bass boosts between 200 and 400 Hz for more punch and roundness (especially on digital multitrack recordings); and upper mid or treble boosts between 1 and 8 kHz to increase overall brightness and to aid the projection of vocals, guitars, drums, and solo instruments. EQ increases in the 400 Hz to 1 kHz range are rarely needed due to the fact that most microphones and monitors exhibit fairly even response in this region. However, increases in this range, when used cautiously, can bring out chordal instruments, warm up vocals, and make thin-sounding mixes bigger.

You may choose to do corrective EQ in the computer rather than during the transfer. Certainly the precision, affordability, and high quality of many equalization plug-ins (not to mention the allure of multiple undo levels) make this an attractive option. If you plan to EQ in the computer, keep your input levels a little lower during the transfer to allow for potential signal boosting and the subsequent increase in gain it may produce. Any overall gain changes, normalization, or compression should be done after all EQ decisions have been made. If you need to equalize a normalized region, avoid digital overloads by dropping the overall gain of the track by 2 or 3 dB before adding EQ. This is an excerpt from the following article: Electronic Musician Mastering Continuity.


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