CD mastering is an art and a science

Mastering is the final creative and technical step prior to pressing a record album (CD, DVD, cassette, or other medium). Compare CD Mastering to the editor's job of taking a raw manuscript and turning it into a book. The book editor must understand syntax, grammar, organization and writing style, as well as know the arcane techniques of binding, color separation, printing presses and the like. Likewise, the CD Mastering engineer marries the art of music with the science of sound.

The Craft of CD Mastering.
The audio mastering engineer is a specialist who spends his or her entire time perfecting the craft of mastering. Audio mastering is performed in a dedicated studio with quiet, calibrated acoustics, and a single set of wide-range monitors. Signal paths are kept to a minimum and often customized gear and specialized tools are used. The monitors should not be encumbered by the interfering acoustics of large recording consoles, racks or outboard gear. In other words, the acoustics are first optimized, and all other considerations must be secondary to the acoustics. For optimum results, mastering should not be performed in the same studio as the recording or with the same engineer who recorded the work. It is important to find a mastering engineer who will bring his expertise and unique perspective to an album project, to produce that final polish that distinguishes an ordinary recording from a work of art.

What Is A Mastering Engineer?

The CD mastering engineer must have a musical as well as technical background, good ears, great equipment, and technical knowledge. Ideally, he should know how to read music, and have an excellent sense of pitch. He knows how to operate a range of specialized technical equipment, much of which is not found in the average recording studio. The successful mastering engineer understands many musical styles (and there are a lot out there!), edits music, and puts it all together with sophisticated digital processing tools. He is sensitive to the needs of the producer and the artist(s), and treats each project or CD with individual attention. He must understand what will happen to the CD when it hits the radio, the car, or the home stereo system.

Master vs. pre-master vs. glass master
What's the Difference between the CDR and the Glass Master?

Premastering, not mastering, is the more accurate term, since the true master for a Compact Disc is called the Glass master, which is etched on a laser cutter at the pressing plant. In fact, the Glass Master is destroyed during the production process. The only thing permanent is the stamper, a round metal form that can be used to press thousands of CDs before it is replaced. There are two intermediate steps (the father and the mother) before creating the stampers that press your CDs. If you're interested in learning more about the processes at the plant, visit So, we really should label the material that is going to the plant a PreMaster. The material going to the plant may be an Exabyte DDP tape, a CDR (recordable CD), or a PCM-1630 tape. Even though it's really a PreMaster, it's customary to label the 1630 tape or CDR CD Master--because (hopefully) there will be no further alteration of the digital audio at any subsequent stages. If the pressing plant does its job right, the bits on the final CD will be identical to those on the master that left the Mastering House.

Why shouldn't I call my DAT tape the "MASTER"?

The word Master is overused...I've searched record company libraries, and often found several tapes of a record album, each one labelled master, but in reality, there can be only one Master tape. You should label your tape Mix tape, or Original Session Tape or Edited Work Tape, or Edited Compilation, Unlevelled or perhaps Assembled Submaster. But as you can see, using the label Master will only confuse things later on. Other confusions arise when the producer has second thoughts. He may decide to change the EQ or relevel a song, but forget to relabel the previous master. Certainly, the first thing is to prominently print DNU ("do not use") on the label of a newly "obsolete" tape.

Seven Reasons Why Mastering is Needed. Can't I just mix to DAT?

Every recording deserves good mastering. When you're through mixing, your work is not finished. Mastering adds polish, it sounds more than just a record...it becomes a work of art. The songs work together seamlessly, their sound can take on a dimensionality and life that enhances even the best mixes. Here are seven reasons why Mastering is needed.

1. Ear Fatigue Most music today is produced by recording a multi track tape. The next step is the mixdown. This mixdown may take anywhere from 4 hours to 4 weeks, depending on the producer's predilections, the artist's whims, and the budget. Usually each tune is mixed in isolation. Rarely do you have the luxury to switch and compare the songs as you mix. Some mixes may be done at 2 o'clock in the morning, when ears are fatigued, and some at 12 noon, when ears are fresh. The result: Every mix sounds different, every tune has a different response curve.

2. The Skew of the Monitors Monitoring speakers. It's amazing when you think about it, but very few studios have accurate monitor systems. Did you know, placing speakers on top of a console creates serious frequency response peaks and dips? A typical control room is so filled with equipment that there's no room to place a monitor system without causing comb-filtering due to acoustic reflections. And though your heart is filled with good intentions, how often do you have time to take your rough mixes around, playing them on systems ranging from boomboxes to cars to audiophile systems? Usually there is no time to see how your music will sound on various systems in different acoustic environments. The result: your mixes are compromised. Some frequencies stand out too much, and others too little.

3. More Me The producer was supposed to be in charge. He tried to keep the artists out of the mix room. But something went out of control. The producer was gone for the day, or the bassist had a fit of megalomania. Or the artist decided to be his/her own producer. Whatever....all the mixes sound like vocal, or bass, or (fill in appropriate instrument) solos.

4. May I Have Your Order, Please When mixing, you (the producer) often have no idea what order to put the tunes until after all the mixes are completed. If you physically compile these songs at unity gain, and listen to them one after another, it probably won't sound like "a record." Some tunes will jump out at you, others will be too weak; you may discover (belatedly) that some tunes are too bright or weak in the bass, or that the vocal is a little weak, or that the stereo separation is too narrow. These things actually happen, even after weeks in the studio, and the problems sometimes don't become apparent until the album is assembled in its intended order, or auditioned in a good monitoring environment.

5. The Perspective of another Trained Ear The Buck Stops Here. The Mastering engineer is the last ear on your music project. He can be an artistic, musical, and technical sounding board for your ideas. Take advantage of his special ear... many beautiful music projects have passed through his studio. You may ask him how he feels about the order of your songs, how they should be spaced, and whether there's anything special that can make them stand out. He'll listen closely to every aspect of your album and may provide suggestions if you're looking for them.

6. Midi Madness Lately it sounds like everyone is using the same samples! Acoustic sounds are coming back in vogue, but perhaps you haven't got the budget to hire the London Symphony. So, you had to compromise by using some samples. But you shouldn't compromise on mastering. Good mastering can bring out the acoustic quality in your samples, increasing your chance of success in a crowded music field.

7. Don't Try This At Home The invention of the Digital Audio Workstation (DAW) and the digital mixer is an apparent blessing but really a curse. Many musicians and studios have purchased low cost DAWs and digital mixers because they have been led to believe that sound quality will improve. Unfortunately, it's real easy to misuse this equipment. We've found many DAWs and digital mixers that deteriorate the sound of music, shrink the stereo image and soundstage, and distort the audio. There are several technical reasons for these problems-usually wordlength and jitter are compromised in these low-cost systems. Therefore, we recommend that you protect your audio from damage; use a mastering studio that employs a high-resolution system that enhances rather than deteriorates audio quality. Prepare your tapes properly, and avoid the digital pitfalls. Use the informative articles at theDigital Domain web site as resources to help you avoid audio degradation. When in doubt, take this advice: mix via analog console to DAT or analog tape, and send the original tapes to the mastering house. You'll be glad you did.

Those are only some of the reasons why, inevitably, further mastering work is needed to turn your songs into a master, including: adjusting the levels, spacing the tunes, fine-tuning the fadeouts and fadeins, removing noises, replacing musical mistakes by combining takes (common in direct-to-two track work), equalizing songs to make them brighter or darker, bringing out instruments that (in retrospect) did not seem to come out properly in the mix. Now, take a deep breath and welcome to the world of CD mastering.

Analog versus Digital Processing in Mastering

Earlier in this article, I cautioned against returning to the analog domain once you've converted to digital. Ideally, you only want one of these conversions, once in the original recording, and once in the CD player playback.

But what about Pultecs, tube and solid state equalizers, tube and solid state compressors, limiters, exciters.... Most mixing engineers can cite a plethora of famous processors that perform their work with analog circuitry. While useful for effects patching during a mixdown, a good number of these processors are unsuitable for mastering purposes. For example, an old, unmaintained Pultec may be a little noisy, but still be suitable to process a vocal or instrument during a mixdown. But would you pass your whole mix through that noisy box (maybe yes, if you like the sound!)? However, every processor used by a mastering studio (a good mastering studio) will be used in matched pairs, have calibrated positions, be quiet, clean, well-maintained. Calibrated positions are important for re-mastering, or for revisions. Clean means low-distortion and noise. Matched-pairs keeps the stereo image from deteriorating.

If a mastering engineer has a favorite analog EQ, or processor he wishes to use to create a particular sound from a DAT tape, he should carefully balance out the cure versus the disease. There is always a loss in transparency when passing through analog stages, particularly A/D/A. Anyone who has patched processors in their Consoles is aware of these tradeoffs. In other words, you have to carefully weigh the veil and fogginess that results from patching the DAT via analog versus the changes the processor can give versus bringing the DAT into a high resolution Digital editing and mastering system and performing the processing in the digital domain.

There will be an inevitable slight (or serious) veiling or loss of transparency due to each conversion. However, perhaps the mastering engineer feels the music will benefit from the sonic characteristics of a vintage compressor or equalizer...maybe he's looking for a "pumpy" quality that can't be obtained with any of today's digital processors (many people complain that digital processing is too "clean"...certainly a subject for another essay). There are many vintage "sounds" and other effects that still can only be obtained with analog processors. And finally, some mastering engineers claim that analog processors sound better than digital processors. I'm not one of them; I won't make that blanket statement. But I agree that analog processing is the "bees knees" for many musical productions. For example, I transferred a client's DAT to 1/2" analog tape and then back to 20-bit digital. Why? In short, because it sounded better. The analog tape stage did just the right thing to the source. I also had to make the fine choices of tape type, flux level, speed and equalization. Each of these decisions helped attain the spacious, warm, yet transparent sound quality my client and I were looking for. Ultimately, we used (and preferred) the analog dub to the original digital source for 8 out of the 10 tunes!

Even without going through the analog tape, I have always maintained that A/D and D/A conversion processes are the most degrading processes that can be done. When we think about using an analog process on a digital tape, the first thing I ask the producer is "why didn't you mix to analog tape in the first place?" Then there would be less questioning about which route to take. When we do go back to the analog domain, I use the highest-quality 20-bit D/A converter (works well even on 16-bit tapes), carefully calibrated levels, short analog signal paths and quality cables, and when converting back to digital, an extremely high-quality 20-bit A/D converter. Then, the losses in transparency due to conversion will be minimized, and in many cases we consider the improvement due to the unique analog processing outweighs the losses of an extra D/A/D conversion.

Most of the time, I personally have found the digital process to be the most transparent of the two options. Perhaps this is because I am very comfortable in both the analog and digital domains. Other mastering engineers agree or disagree with me on this point, and our choice of processing depends a lot on personal taste, habits developed over the years, ignorance (or knowledge) of the power of good digital processors, the quality and transparency of their monitoring system (if it doesn't show the degradation, then maybe it isn't there?), and so on. I have many clients with excellent ears who cannot believe that these results were obtained with (god forbid!) digital EQ and processing.

Unique Digital Processes

There are also some unique (and proprietary) techniques that I perform only with 24-bit DSP, one of which I call microdynamic enhancement, and the other I call stereoization. If the material needs it or warrants it, these processes can only be done in the digital domain.

For example, my invention, called microdynamic enhancement, can restore or simulate the liveliness and life of a great live recording. I've used it to get more of a big-band feel on a midi-sample-dominated jazz recording. I've used it to put life into an overly-compressed (or poorly-compressed) rock recording. It's really useful and extraordinary in helping to remove the veils introduced in multi-generation mixdowns, tape saturation and sound "shrinkage" that comes from using too many opamps in the signal path. My microdynamic enhancement process is achieved totally digitally.

I've invented another totally digital process called Stereoization, which I use on unidimensional (flat-sounding) material, often the sad result of low-resolution recording and mixing. Stereoization is very different from the various width-altering processes that are now-available. And now, we are proud to announce that Stereoization is available to all mastering engineers, with the patent-pending K-Stereo Processor(TM), manufactured by Digital Domain and introduced December 2000.
Stereoization actually captures and brings out the original ambience in a source. The degree of stereoization is completely controllable. Instruments in the soundfield have natural space around them, as if they were recorded with stereo microphones. The process is totally natural, utilizing psychoacoustic principles which have been known for years, and it's fully mono-compatible.

The above special processes can only be achieved digitally. And DSP engineers are constantly inventing new ways to simulate all the traditional analog processes. So there's a lot to be said for digital processing, and I have no doubt that will become the dominant audio mastering method in the next five years. Whether analog or digital processing is the better choice today is very dependent on your music, and the talents and predilections of the individual mastering engineer. In many cases we use a hybrid of analog and digital processing techniques to produce the best-sounding master.

Before Mastering: Mixing, Editing, and Tape or File Preparation

Of course, before you get to the mastering stage, there is the mixing stage, which may be followed by an editing or processing stage. Many of you have purchased one of those new digital mixers to "stay in the digital domain" from beginning to end; many of you may have purchased a DAW (editing workstation) to prepare your tapes or files.

After mixing, it's time to prepare your materials, and possibly edit:

If you mix to analog tape, the best thing is to make a safety digital copy, edit the analog (if necessary) with a razor blade, and send the original tape to the mastering house. A 30 IPS, 1/2" two-track tape contains a wide frequency and dynamic range, and is a superior recording medium. Some will argue that analog tape is more pleasant sounding than 44.1 Khz 16-bit digital tape (is that why are so many of us are nostalgic for the sounds of the 50's and 60's?). My essay called Back To Analog talks about those sonic differences. But the newer digital formats record at 20-bit, at 44.1 Khz sampling or 48 Khz, with 4-tracks (good for surround sound), or at 96 Khz (the first editing systems for 96 Khz have just appeared, as have good sample rate converters that support this format). We are living in very interesting (and expensive) times

A to D conversion is the weakest link in the recording chain. Repeated copying via A/D/A can result in a subtle (or obvious) veil and/or harshness in the sound. That is why, if you prefer mixing to 16-bit digital tape (DAT), you should obtain the best-quality external A to D Converter available, one that is properly-dithered to 16-bits. Even when dithered to 16 bits, a good 20-bit A/D is sonically far superior to any converter built into a DAT machine. Once we have received a digital tape, we almost never return to the analog domain*. Ideally, your digits shouldn't hit a D/A converter again until they reach the consumer's CD player. That means if you want to use a Pultec, LA-2, or other analog "processor", please use it during the mixdown. Interestingly, some mastering houses now have digital equalizers (and processors) that do a very good job of simulating the sound of the venerable Pultec, only in the digital domain.

So, with few exceptions, be sure to keep your sound in the digital domain once it has crossed over the line. What about digital copying? What about digital editing, level changing, equalization or other processing in the digital domain? Please leave post-processes such as these to the mastering house. Here are some of the reasons why...

Question Authority...

Surprisingly, the little bits on your tape can undergo a perilous journey through some of the digital processors and editors on the market. If there's a DSP inside, suspect the worst until you know for sure. There are some tests you can perform on your digital processors and editors (or workstations) without expensive test equipment. These tests include linearity, resolution, and quantization distortion, common problems caused too-often by digital audio editors.

In other words, while you may be tempted to save time or money by doing preliminary editing with a digital audio editor, be very careful. A digital editor, after all, is just one big computer program; computer programs have bugs (there's not one bug-free program in existence!) and one of those bugs could be guilty of distorting your digits, in a big, or very subtle way. The sophisticated digital mastering systems at CD mastering houses also have bugs, but undergo regular testing to verify proper sound quality. We have received recordings with truncated fades (where the audio sounds like it dropped off a cliff!), distorted audio on the fadeouts; music with poor low-level resolution that is a shadow of its former self; music whose soundstage (stereo width and depth) appears to have collapsed, or recordings that have an indescribable "veil" over the sound compared with their sources. Here are some pointers that will help you avoid these problems:

Don't wreck your digital tape...

• STOP right here if you want to re-order your tunes before sending them to the mastering house. You won't save time copying your DAT or reordering it in an editing system before sending it for mastering. If you're not careful, your digital copy (reordered) can have glitches on it. DAT recorders are not perfect, and are subject to dropouts and error corrections.
• Never make just one DAT copy. Always make two at once, and hold onto that safety---never send your only copy in the mail.
• Dubbing procedures: Always listen carefully to the output of the recorder while copying. If you must pause the recorder during the dubbing process, make sure it is rolling in record for at least 10 seconds before the tune begins. This guarantees the tape will play back later without glitches or noises (most DATs can lock up in 1 to 2 seconds, but who wants to play with fire?). Don't stop the recorder until you are sure the music has faded completely--DAT tape is cheap! This means that DAT tapes dubbed from other DATs can never have the short spacing we like on an album. Accept that...it's part of life.
• Yes, it's a good thing to make safety copies and put together some tests to find a good song order, but it's probably better to send the "raw" original mix DAT(s) to the mastering house (along with a good written log of where to find the cuts). There is less chance of degradation or missing a piece, because the people who make digital copies are subject to human error. There's even a bonus in sending the original mix tape, as we now have available outtakes, alternate mixes (vocal up, vocal down, etc.) or other sections the mastering engineer can use to repair noises or problems you may not have noticed. The mastering engineer will reorder the tunes, carefully smooth fadeins or fadeouts, place black or roomtone between the tunes, in extremely efficient time. Plus, at the mastering studio, each fadeout or level will be controlled with dither, a topic worthy of discussion.
• When you mix, leave the tunes long. DON'T fade in or fade out. If you have ideas on how the fades should be performed, give some suggestions to the mastering engineer. The more artistic leeway you give to the mastering engineer, the more room for a better product, because after years of editing and mastering experience, there are things we can do that you may not have considered. For example, I've got some tricks that can create real-sounding endings on tunes that everyone thought had to be faded.
• At the ends of songs, leave all the decay you can, because the mastering engineer has precise digital tools for performing artistic fades. He may even suggest a segue (where two musical pieces overlap) as an artistic alternative. Remember, editing is like whittling soap. You can remove a piece, but you can't restore what's been chopped off! However, there are some tools for adding tails. If, for example, the musicians talked before the ringout was over, or the bass player dropped his bow , or the assistant stopped the recording before he was told, there are ways to add convincing tails to a song that are indistinguishable from real life, and sometimes even better!
• Noises: Alert the mastering engineer to any noises that bother you (abs time on the DAT) and we may be able to remove them with No-Noise (TM-Sonic Solutions). Conversely, some noises might sound good if left in, producing a "relaxed, easy going feel" to an album. This includes countins, sticks, verbal comments by the musicians, and so on. Note any that you think are useful, and we may find that certain noises help to glue the album together.
• If you have complex editing that you would like to perform first, proceed with caution. TEST YOUR EDITOR first, also test it with a bitscope. Do this for each software revision. You really can't trust a manufacturer when your precious music is at stake. Listen carefully for degradation of soundstage width and depth, graininess, increased brightness or hardness. Listen on the finest reproduction system possible, or these changes may be perceived as too subtle and you won't know you've ruined your material until it's too late! You're welcome to send us a preliminary tape before you mix all your tunes. We will check it for tonal balance and for digital errors before you proceed.
  
• "Don't try this at home!" This one is about maintaining the sound quality of your digitally-recorded music. Let's keep those little aural tickles you mixed so carefully into your music. If you're going to edit digitally, and if your digital editor passed the tests, please do NOT change the gain on your music. Do not raise it or lower it. Don't perform any fadeins or fadeouts! Don't use any of the fancy "plugins" that "maximize" the sound. Don't equalize or compress using the DSP in the editor. Don't normalize. Don't pass through external digital processors (including digital reverbs or compressors). And finally, turn the DITHER (if available) off. Every one of these processes can deteriorate sound, especially if the tape is to undergo further digital processing. Cumulative digital processes (if improperly performed) can be very degrading to sound.
• Here's why: The reason (and many engineers are not aware) is that almost every DSP computation adds additional bits to the wordlength. The wordlength can increase to 24, 56, or even 72 bits. The right thing to do is keep your newly "lengthened" words as long as possible, until the final stage, where they will be dithered down to 16 bits for the CD. So, if you work with a 16-bit editor, and change the gain, for example, you are actually truncating and distorting your sound. Even if the editor has built-in "16-bit dither", you are adding a subtle veil to your sound. 16-bit dither should be reserved as a one-time only process at the end of the chain.
• What makes the CD mastering house different? All the processors at the CD mastering house produce 24-bit output words whenever possible. If the mastering engineer employs digital processing on your tape, he/she will endeavor to keep your tape in the 24-bit domain until the final stage. When properly applied, 24-bit (and longer word) processes maintain a degree of warmth and space that is hard to believe. And that's why it can sound so good! A good, experienced mastering house tests each processor they use for resolution, distortion, jitter, and overall sound quality, auditioning in a superb acoustic with excellent monitor loudspeakers. Use the Mastering House like a mothership, ask any questions you like, because our sole job is to make your recording the very best it can sound.

II. GUIDELINES FOR PREPARING TAPES and FILES FOR MASTERING

This is in three parts: A:General Information, B:Preparing Tapes, C:Preparing Files

A: General Information

DigitalDomain is dedicated to reproducing your music with audiophile quality. If your source tape requires editing, sequencing, spacing, assembling from different reels, equalization, leveling, or other processing, we will transfer analog tapes to 20-bit digital for premastering in our Sonic Solutions Mastering System, or load your digital tapes with maximum resolution entirely in the digital domain. Word lengths of your source are not truncated, and we use the maximum output word length of our digital processors.

Before the Mastering Session/Communicating Your Needs to Us: Each type of music requires a different approach. Often you may find it difficult to communicate what you are looking for in words. If you cannot be here at the mastering session, we will make a special effort to understand what your music is communicating. We will give you our feeling of how your music is sounding as we begin to try an approach. We do not "automatically" equalize. Many fine pieces of music are mastered flat (no equalization) and without additional compression or levelling. But almost every tape that arrives can use a little polish before it walks out the door. You are welcome to suggest or mention a CD of similar music that appeals to you. After the mastering session is over, you will receive a reference CD that you can check on your own playback system (there's no substitute for the system you know), and, if necessary, suggest further revisions or improvements.

Vocal Up/Vocal Down: It's not always easy to get the vocal level just right in a mix. When it's "just right", the band is up there swinging away, and the vocal has enough presence to come through but without taking away the energy from the background. And often in mastering, we may find that the song may be better served if we use a vocal-up or vocal-down mix due to the processing used in mastering. If you're running automation, then it doesn't cost anything to also run a vocal up (1/2 dB or 1 dB, or both if in doubt), and possibly a vocal down mix. This can save myriads of time later.

Stems or Splits: Another valuable approach is to send STEMS, also known as SUBMIXES. Always include a full mix, then, for example, a MIX MINUS VOCAL and a VOCAL ONLY. Or any other split element that you consider important. When in doubt, give us a call before you produce your split mixes. While it's possible to send split mixes on a DAT or analog tape, split mixes are only practical All files must be the same length, and synchronized for this to work well and easy. This means if the vocal-only version has 1 minute of blank at the head, so be it!

Maximum Program Length
The final CD Master tape, including songs, spaces between songs, and reverberant decay at the ends of songs, must not exceed 79:38. We can determine exactly how long your CD will be after editing and master preparation. Masters above 74:30 require special, more expensive media.

B: Preparing Mixdown Tapes and Discs

Labelling your tape or disc

About half the tapes in a typical library are labelled Master that should have some other label. You can imagine it gets pretty confusing separating the elements from the final master if things don't have the proper label. There is only one MASTER for an album, and that is the final, PQ'd, equalized, edited, spaced, and prepared tape or disc that needs no further work, and is ready for production. Only properly-formatted PCM-1630 tapes, Sony 9000 cartridges, DDP Exabyte tapes, and CDRs can meet those qualifications. A DAT is not a CD master. Please label the tape or disc you are sending for mastering: Submaster or Work Tape, or Mix, or Final Mix, or Session Tape, or Edited-Mix, or Compiled-mix, or Equalized Mix, to name several possibilities. This will avoid confusion in the future when revising a work, when looking through the tape library for the real master.

It's so easy to confuse or lose a disc or a master tape. Hand-Label your tape, hard disc, CD ROM or DVD-ROM with the following:
1) Album Title, Artist, Contact phone number, date, and tape number (e.g. "Mix Tape 1 of 2", or "Mix Disc 1 of 4")
2) Disc format, that is ISO-9660 or Mac or UDF, or Masterlink CD
3) Technical information: Sample rate (e.g 48 kHz, 96 kHz, etc.), wordlength (e.g. 24-bit, 16-bit), file format (e.g. WAV, AIFF, SDII, BWF, interleaved or split), channel order if surround (e.g. L, R, C, LFE, LS, RS; or L, R, LS, RS, C, LFE).

Digital Domain accepts all standard tape formats.

Acceptable tape formats

Analog tape 1/4" or 1/2", 30 ips, 15 ips or 7 1/2 ips, Dolby A, Dolby SR or DBX type 1, IEC, AES or NAB equalization. Begin and end the reel with some "bumper", followed by leader. If possible, put leader between songs (except for live concerts and recordings edited with roomtone). Tape should be slow wound, tails out. Label each reel with the album title, song titles, running times of each cut. Indicate tape speed, record level for 0 VU in nw/M, record EQ (NAB or IEC), track configuration, and whether it is mono or stereo.

Include alignment tones of 1kHz, 10kHz, 15kHz, and 100Hz plus (highly recommended) 45Hz and 5kHz at 0VU (on 15 and 30 IPS tapes. Also highly recommended is a tone sweep (glide) from 20 Hz through 500 Hz. Call for information about tones on 7-1/2 IPS tapes). Needless to say, the tones must be recorded by the same tape recorder that recorded the music, and ideally, record the tones through the same console and cables that were used to make the mix. If you find the console meter is not flat when sending tones through it, then have a technician check the console before proceeding. Put the tones at the head of reel one or on a separate reel. Indicate type of noise reduction. The tones should be recorded without noise reduction.

Many historic analog tapes do not include proper tones and sometimes it is not possible to put tones on new masters. If it was not possible to lay down tones on the session, then we will use sophisticated methods to guarantee azimuth and equalization accuracy.

Indicate the proposed order that the tunes will be on the CD, either on a separate sheet, or in a column on the log sheet.

What Sample Rate Should I Use?

Sample rate for all digital sources (tapes and files). The state of the art of converters (A/D, D/A and sample rate converters) has improved exponentially in the past five years. Five years ago, considering the abysmal state of converters, I would have recommended that you try to work at 44.1 kHz if possible, and try to send us a 44.1 K DAT. THIS IS NO LONGER TRUE. My current recommendations are for you to work at the highest possible sample rate and longest wordlength available to you. However, if you are mixing digitally, do not sample rate convert yourselves, to avoid additional degrading DSP. In other words, if you are mixing digitally, remain at the same sample rate as the multitrack. If you are mixing with an analog console, there is a marginal advantage to using a higher sample rate mixdown recorder than even the multitrack. For example, if you are using a Radar 24 at 48 kHz with an analog mixing console, and mixing to the Masterlink, you'll get better-sounding results running the Masterlink at 96 kHz, 24 bit. In the mastering, we would remain at 96 kHz until the very last step.

How to Prepare Your Digital Tape

DAT (Digital Audio Tape) 44.1kHz or 48kHz sampling rate, preferably 48 kHz, since most lower-cost A/D converters sound better at 48K. Include a cue sheet or label the DAT J Card with album title, song titles, start time of each cut (in abs time), or length of each cut if DAT cue times are not available. If possible, put a numbered start ID before each tune and log it on the cue sheet. Start IDs do not have to be exactly placed, but they serve as an excellent guide to telling us that we're copying the proper tune.

Always make and keep a digital backup (clone) before sending a DAT for mastering. If possible, record tone at the head, a calibration tone of 1kHz at a digital reference level corresponding with console 0 VU (this may be anywhere from -14 dBFS to -20 dBFS.). Other frequencies are optional. We use the tones on the DAT to check the condition of your A to D Converter and frequency response of your system.

Begin recording the music after approximately the 2 minute mark (this will pass any possible bad tape which may be at the beginning of the DAT). Put your tones at the head, without Start ID's, and at approximately the 2 minute mark, the first tune with ID #1.

There is no need to sequence or reorder the tunes on your tape according to the album. Just provide a separate list of the final album order and log your tapes carefully. Some producers give us a separate sheet with instructions on which takes to use and where they can be found on the mix tape(s). If you have special requests (such as segues), or tunes that you want to put very close to one another, then indicate them in that letter, or in a discussion with the Mastering Engineer.

When mixing to a digital format (such as DAT), start recording your DAT for at least 10 seconds before the music begins, and keep the DAT rolling for at least 10 seconds after the music ends. This is to avoid potential digital errors when we load in your tape for mastering. In fact, it's best to keep your DAT in the order you mixed the tunes, to avoid human error. Contrary to popular belief, it is not necessary to put the IDs exactly at the beginning of each cut. Don't waste your time doing that. We use the IDs only to help identify tunes. A different process during mastering, known as pq coding guarantees that each track on the CD will begin at the proper moment.

Sony 1630 digital tape (3/4" U-Matic)

Tape must be striped with continuous SMPTE time code, non-drop frame mode at 44.1 kHz sampling rate. Record a minimum of one minute digital black pre-roll and a minimum of one minute digital black post-roll. Include a copy of the Cyclical Redundancy Count (CRC) report. Include a frame-accurate running time log.

C: Preparing Files

CD-ROMs.

Many clients are now sending us CD ROMs with 24-bit WAV or AIFF files for us to master. The first time you cut a CD ROM is a bit intimidating... if there's a problem with your discs, we'll let you know. Why not send a test disc in advance with one file on it and we'll check it for you at no charge!

Simplified instructions for Pro Tools Mac Users:

1) Mix your material in Pro Tools sessions, preferably, one session per song. Remain at 48 kHz (or whatever your original multitrack sample rate is), do NOT sample rate convert. For example, if your Pro Tools session is at 96 kHz, then mixdown to 96 kHz files.
2) Start the songs at 1 or two seconds into the file, not at zero time, and/or start your bounce to stereo, 24-bit, starting a second or more before the downbeat to a second or more after the end fade is totally gone. Bounce to Interleaved AIFF stereo, BWF, or WAV. (Any other format is less convenient and more time-consuming on our end).

3) Collect all the good mixes in one folder, naming or renaming them by the names of the songs (you'll appreciate this later as you sort through them all)! Please do not add any file extension and do not use periods or the / or the character in the name. On the PC we use a utility which can read Mac-format CD ROMs (MacOpener) which automatically supplies an extension based on the Mac resource fork.

4) Get a copy of Toast Titanium and a box of name brand discs with dark green or greenish blue-color dye, (anything but yellow-gold) preferably 74 minutes. Taiyo Yudens are best, but Sonys, Fuji, Mitsui, and HHB are also good brands.
5) When it comes to cutting in Toast, select "Write Disc" (not "Write Session"). Cut a Mac HFS CD ROM, of all your mixes, at 2X speed, no faster, no slower (on the average, this is the best speed for least media errors). If you're absolutely certain your writer produces low errors at 4X, then you may use 4X speed. Send it on. That's it!

Detailed Instructions for those who would like to get it right the First time!

As Bob Ludwig says, " Never turn your back on digital! " Here are some important things to consider:

• DO NOT USE PAPER LABELS! Stick-on paper labels may look impressive, but they increase error by altering the rotational speed of the disc, especially at fast speeds greater than 2X, or with multitrack files, high sample rates or long wordlengths. CDRs that have paper labels are prone to glitches, repeats and noises. Besides, paper labels can become partly or completely unglued over time and come off in the CD reader, which is not a pretty sight!
• Please leave some space (at least 1 second) within the file in front of the music modulation. Do not chop it tight--- because a lot of programs that read or write files of this type put glitches or noises at the head, and that's not nice!
• Please use fixed-point 24-bit format (also known as "Integer Format"). Do not use floating point files, as there are many incompatible floating point formats and we just can't read them all! (e.g., do not use 32-bit floating point for the file you send for mastering).
• The sample rate can be any standard rate, up to 96 kHz.
• Please FINISH (close) your SESSION --write a complete (final session) CD ROM. If you did not "close" your disc, then we have to jump through hoops to read it. Check that your disc is readable by mounting it in a regular CD ROM. Make sure all the files show up in the directory.
• Interleaved is preferred over split mono, because it makes it easier to guarantee the stereo (or multichannel) sync. If you must use split mono, then identify the channels, e.g., Love Me Do-1 for left channel and Love Me Do-2 for right channel. (Don't use a . character because the PCs will get confused and think the .1 is an extension!).

Preventing Those CD ROM Glitches! For us to get a good clean ROM read means you have to make a good clean write (recording). Glenn Meadows CDR Tests apply to CD ROMs as well as audio CDs. Please stick to known media and write speeds that are known to produce low error rates with your writer, typically 2X to 4X. Avoid the yellow-gold media (color of the writing surface), especially the gold media with the "K----" brand. The gold media seem to require a unique writer to give good results, perhaps only the "K----" brand writers work. That why we recommend the media which is optimized at low writing speeds---media which usually has a dark green, or greenish-blue tint, perhaps with a hint of yellow. Remember, the substrate (metal part) can be gold, but the chemical layer on the writing side (bottom) should be blue or green as mentioned. But not all brands are alike. Test your precious files before sending them; try playing one back, in real time, from a CD ROM reader. Or try copying a file back to your hard disc. If you get file read errors, then you know you're in trouble. CDR blanks have also recently become a commodity. The problem is that not all blanks are alike, and the "drugstore brand" does not perform well. USE 74 MINUTE BLANKS IF AT ALL POSSIBLE SINCE VERY FEW current brands of 80 MINUTE BLANKS perform adequately. And since all the stores are now carrying blanks, and the 74 minutes have disappeared due to marketing pressure, call your professional distributor and ask for a high-quality name brand professional 74 minute blank. I don't often recommend brands, but I must say that the first manufacturer of CDR blanks, and still one of the best and compatible with most all writers is Taiyo Yuden, which can be obtained from professional distributors.

III. 24-bit digital formats...So Many Formats, So Little Compatibility

If you have the opportunity to mix using a 20-bit (or 24-bit) A/D converter, we'd love to receive it in a digital medium that retains this information. At this time, there is no single standard format to store 24-bit data. No mastering house could afford to own all the present (and provisional) formats that can handle this data.

New tape and file formats: If we do not yet have the format, we will either rent or obtain it to satisfy the best needs of your music project. If this is your first time sending audio files to us, we advise that you create (mix) one short tune and send the file to us on CD ROM or removable disk. You'll be glad you did. Many people will be shocked to learn that their so-called "24-bit" files have been truncated by their hardware or software to only 16 or 20 bits. We will examine your files for resolution and recommend how to proceed if we discover your files are not what you thought they were!

Who are the candidates for high-bit data interchange?

1/2" or 1/4" Analog Tape. The resolution, purity of tone, clarity, depth, and transparency of a 2-track, 1/2" 30 IPS tape are hard to beat, especially when reproduced on customized, high-resolution electronics. Yes, analog tape is euphonically colored, but to my ears, it captures more of the depth and space in the source. A good analog recording has a three-dimensional character which cannot be obtained with "cheap" digital. Depending on the music, it's debatable whether 96 KHz/24-bit digital sounds as good as fine analog. Analog tape is universal, can be played on anyone's tape recorder, and will archive for 25-30 years. This is still your best bet for affordable, good-sounding, and universally compatible "high-bit" interchange.

ADAT type II (formerly known as "Meridian"). This machine stores 20-bits on tape, not 24. It has the potential to make very nice recordings with its internal 20-bit A/D or a high-quality external A/D.

I Coulda Been A Contender. I asked Don Hanna, engineering liason of Alesis, why the company decided to make the ADAT type II as a 20-bit machine instead of 24-bits. He responded, "it is very important to maintain robustness and reliability in a tape recorder. We found there was enough room in the ADAT standard to make a 20-bit recorder, but data reliability would have been compromised if we tried to squeeze 24-bits/8 tracks on 1/2" tape." Pity, because with Alesis's clout, this machine could have been the contender for the new 24-bit interchange standard. Hanna stated that the expansion slot on the back of the machine will permit a "Paqrat-like" modular accessory, which might cost $600 to $1000. The module will turn the ADAT II into a 6-track, 24-bit recorder. Sadly, that sounds so esoteric to me that I doubt it will have the force to become an interchange standard, especially on top of the ADAT II's premium price.

ADAT Type I or DA-88 tape with Prism MR-2024T process or Rane Paqrat Process. Prism and Rane deserve praise for manufacturing these "bit-splitters", which turn a 16-bit 8-track machine into a 4 track/24 bit or 6 track/20 bit recorder. But this is a "niche" product-like all adapters, they're awkward and expensive unless their purchase cost can be justified on more than the occasional project. However, a new turn of events from Yamaha may turn this rare technique into a commonplace standard. Yamaha has just announced an upgrade to their O2R console firmware which allocates 24 bits worth of information to two adjacent 16-bit tracks. Once a company with enough market force (like Yamaha) implements a standard, others will follow. Unfortunately, the three bit-splitting standards are not mutually compatible. I hope that Prism issues an upgrade to their adapter which makes it compatible with the Yamaha format, so the mastering house will not have to have an additional expensive console around just to make transfers.

Alesis Masterlink M2000 High Resolution Master Disc Recorder. This is a wonderful format that's vying to be the standard. The best part about this recorder is that it makes standard, fully-compatible AIFF files in CD ROM (ISO-9660) formats (see immediately below). This is a ubiquitous format that any CD ROM reader can read and most mastering houses can translate or play with an appropriate translation program. The recorder will support sample rates from 44.1 kHz-96 kHz, and make standard audio CDs as well as CD ROMs with 24-bit files. The only down side is high sample rate files take up a lot of space, but at least CDRs are inexpensive.

This machine purports to offer "finishing tools" for preparation of CD Masters, which gives the impression that a finished master is as simple as applying compression, equalization, and pressing a few buttons. There is no such thing as a stand-alone "finishing tool". The ultimate "finishing tool" is a skilled, experienced mastering engineer working in a calibrated environment, capable of applying his/her experience to the creation of a superior, finished album. Use the Masterlink to make "demonstration" or "roughs" prior to sending the raw sources for mastering.

CD ROM (ISO-9660) with 24-bit AIFF, SDII or WAV files. CD ROM is a very powerful, cross-platform interchange standard. AIFF, "Apple Interchange File Format", is the de facto standard in the Macintosh world. Gold CDs are reliable (if you keep them out of the sunlight), but you need a computer with 24-bit input and storage, a CD writer, and the software to write 24-bit AIFF files. Capacity is only 650 MB (43 stereo minutes), so files will often have to be split between disks. Sonic Solutions versions past 5.3 include 24-bit AIFF support. Everyone will eventually support 24-bit AIFF, since DVD has increased demand for high-resolution file interchange. Please use Interleaved format for stereo files although we can accept dual mono files if necessary. Standard formats include: AIFF, WAVE, or Sound Designer II. As we move into surround sound, multitrack formats will become popular, such as the Pro Tools Session format. Please follow the preparation etiquette mentioned in the preparation section (above).

8 mm tape. 1) DDP-24 bit. Non-existent, at the moment. Since DAW manufacturers succumb to the "not invented here" syndrome, independent Doug Carson associates, who has no axe to grind, may create the universal data-interchange standard. The emerging DVD disc will require a revision of the DDP standard. Eventually, DDP-24 bit, on either 8 mm (Exabyte) or DLT tape, will become an international standard. Thus any mastering system will have to create, read, and load-in from masters in DDP-24 bit format. This will instantly make Sonic, Sadie and everyone else cross-platform compatible. Sonic Solutions already use Exabyte drives for archiving, so this lightweight, portable, high-capacity format has great promise.

2). Sonic Solutions Archive. A very nice data interchange medium, if you own a Sonic System. It's already 24-bit compatible, and contains built-in error correction and indication. We've received one archive from a client, who was very pleased with the digital mastering techniques we can apply to his 20-bit pop recording.

Genex or Studer MO disk. You get a lot of value for your money with these new standalone MO recorders. For around $9000, the Genex GX8000 provides 8 tracks of 20 bit/44.1/48 K, 6 tracks of 24 bit/44.1/48 K, or 2 tracks of 88.2/96 Khz/24 bit or 4 tracks of 88.2/96 Khz/20 bit. (But no A/D or D/A converters, those are extra). Through lossless data compression techniques (requiring an external adapter, not yet invented), this recorder could store 4 tracks of 96 KHz/24 bit. We have to see the reactions of the early adopters. If the Genex/Studer format becomes a standard, then DAWs will have to support this MO disk. Sadie leads the way in compatibility, largely because their file format is DOS-compatible. They can already read Studer 16-bit MO disks directly, but not 24-bit because Studer's 24-bit format is not DOS standard. Tragically, Genex is not DOS standard at all. To read Genex disks, you have to connect the Genex machine to the Sadie SCSI bus, then you can transfer 24-bit files in either direction at 4X speed. Unless someone invents a translator to read Genex or Studer 24-bit disks directly, the MO situation remains a definite mixed bag. This machine has the potential to become a recording standard because of its high price/performance ratio, versatility and reliable MO data storage, though some engineers balk at the price, and perhaps they're right, considering what Yamaha now has to offer (see below).

Hard disk. A hard disk is a lot more awkward to transport than MO removable cartridges. Besides transport weight and bulk, the real problem is file format. The only 24-bit files you can exchange with a Sonic system are Sonic native files and AIFFs. The situation is much better in the Sadie camp. Sadie's hard disk is immediately DOS compatible with several other PC-based sound editing programs. You can even mount a foreign-format hard disk in the Sadie and begin editing. But I suggest you confirm 24-bit interchange compatibility with the vendor of your DAW. Sadie's audio file interchange supports Lightworks, WAV, IDS (a new common file for Europe), Filmwave, but surprisingly, not AIFF (the Macintosh standard). We'll have a small increase in productivity if Sadie can use disks with AIFF files, and Sonic starts reading 24-bit AIFFs. I've heard rumors that Sadie will support AIFF shortly...what a story: instant Mac/IBM soundfile interchange!

Several newly-announced hard-disc recorders, from Yamaha, Tascam, and Mackie, will also be contenders for data interchange formats. Perhaps a hard disc with Pro-Tools compatible files will become the medium for exchange. Stay tuned (see under indiidual brand names).

Nagra D. The world's most reliable, beautiful, and expensive (approaching $30,000) 4 track, 24-bit recorder at 44.1/48 KHz, or 2 tracks at 88.2/96 KHz. I love this machine. Can't afford it, but maybe someday. Cost is the obstacle to making this machine the standard for interchange.

Pioneer 88.2 kHz DAT processed with dB technologies dB 3000S. dB technologies very cleverly designed a system that will squeeze 24-bits of information on a 16-bit DAT by running the DAT at double speed and making a pseudo 88.2 KHz tape. I think it's too esoteric to become an interchange standard. But thank you, dB Technologies, for proving the impossible can be done.

Prism DRE process (only produces 18-bit output words). The Prism A/D converter has a lossy data compression option which squeezes long words onto a 16 bit DAT. A complementary decoder is required. You can use Prism's A/D with the encoder, or go into the encoder with a digital console's 24-bit output. DRE sounds very good, but it's not quite 20-bits worth of quality to my ears, perhaps 18-19. Transients are slightly muted, but in a very pleasant way, making it an excellent mid-price recording solution, much better sounding than 16-bit. The combination of the Prism A/D and a DAT machine is probably the most economical high-bit recording medium around.

Sony PCM-9000 MO disk. At $14,000, this machine is not exactly cheap. But it records 24 bits, it's very dependable, sounds very good, and will be supported by this company. They're talking about a double-speed retrofit which will support 96 KHz. A standard, though? I doubt it. Quality of construction and lack of maintenance are important considerations, but it's not like the old days, where a Studer analog tape recorder (built like a truck) paid for itself in reduced maintenance. The major moving parts in today's hard-disk-based recorders are in inexpensive computer disk drive mechanisms. The 2-Track Sony is a beautifully-constructed, rugged machine, but is it worth $5,000 more than the 8-track Genex? Compared to the Genex 8 track MO or the new Yamaha 8-track, the Sony, with only two tracks, costs $5,000 additional. Smart money is betting on the Genex or the Yamaha, unless the price of the Sony machine and media comes down.

TASCAM DA-45 HR 24-bit DAT Recorder. This new "compatible" format is a no-brainer. Why should anyone replace their aging DAT machines with an ordinary 16-bit DAT recorder when the new 24-bit format is available? It will also play your old DAT tapes. If you're mixing from a digital console, no further work is necessary, just transfer 24 bits worth to the Tascam. If mixing from an analog console, I suggest you buy or rent a high-quality external A/D converter, which will sound better than the converters in the Tascam. Nevertheless, if you're on a budget, the converters in the Tascam, taken at 24 bits, will sound better than the 16-bit converters in the typical 16-bit DAT machine.

TASCAM or equivalent DA-78HR or DA-98HR 8 mm 24-bit. Up to 8 24-bit tracks can fit on this new format. Be sure to use an approved tape tape to avoid dropouts as this format is very particular.

YAMAHA D24 recorder. At the September 1998 AES Convention, Yamaha announced a new, affordable (under $3000) 8-track, 24-bit recorder using Jazz and other SCSI hard drives. First shipments are expected late-1999. This could easily become a new interchange and recording standard, if the machine proves reliable. Plus, the recorder handles multiple tracks at various sample rates.