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Why we have mastering and how we got here from there

by Robert Auld

This is an adaptation of an article that originally appeared in Recording Magazine in 2004.

In the beginning there was no such thing as mastering a record, as a separate discipline. If you were a recording engineer, your recording machine was a disc cutting lathe. Prior to 1925, this tool of our trade was rather primitive--the cutting stylus was connected to a diaphragm which was powered by a large acoustical horn and the turntable motor was spring powered. By the 1930's electricity had entered the picture and that newfangled invention of the radio studios, the microphone, drove the cutting stylus through an amplifier. Regardless, the wax discs you cut were then used to make stampers from which shellac-composite 78 rpm discs were pressed. This was record production before tape.

After World War II, tape recording and the micro-groove Lp were introduced. For the first time a separate engineer was charged with cutting master discs from the recording session tapes. He was not necessarily called a "mastering engineer" however; sometimes the terms "dubbing engineer" or "transfer engineer" were used. This reflected the belief that the tape to disc transfer was a technical step in record manufacturing, not much different from stamper plating or vinyl press operation. The attitude of many record labels, including some known for their technical excellence, was that the mastering engineer was not supposed to exercise artistic judgement. Here is producer John Culshaw, writing in 1967 about how it worked at British Decca (known in the U.S. as London records) in the 1950's and 1960's:

The dubbing engineer has a long and often thankless task, but he usually appreciates the interest of the producer and recording engineer in helping him to ensure that the sound he is putting on his disk is an exact replica of what is on the tape. This is mandatory, at least in Decca. The methods of some companies who put any old sound on the tape in the hope that it can be "adjusted" or "compensated" at the dubbing stage are not tolerated. The responsibility for the sound always lies with the people who made the tape, and not with some committee of experts who have probably never been near a recording location. (1)

Clearly, Culshaw was working in a world of large corporate record production that was organized differently from what we usually encounter today. The picture he paints of rigorous attention to the technical quality of the sound was probably true for British Decca; in classical music, at least, they were the equivalent of an audiophile label in those days.


Other large record companies of that time had other priorities, especially when it came to pop music production. The trend was to automate the tape to disk transfer as much as possible, in the interest of production efficiency. The first step in this direction was automated margin control, introduced in the mid-1950's, which allowed control of the spacing between the grooves of an Lp by analog computer circuitry. It was definitely a step forward in record production, as it made possible record sides of up to (and even beyond) 30 minutes.

Another problem in mastering the Lp was the tendency of real music to have a wider dynamic range than the system could comfortably accommodate. While recording to tape helped a little, chiefly due to analog tape's tendency to round off sharp high level transients (the tape saturates when hit with too much level), it was still possible to cut to disc waveforms that simply could not be played back--the stylus would literally jump out of the groove--or even to burn out the disc cutter head. The high frequency boost of the RIAA recording curve made this latter event a possibility if the high frequency content of the program material was not carefully controlled.

To protect against expensive events like cutter heads blowing up, and to ensure a more consistent final product, specialized limiters and compressors were developed for use in record cutting. By the mid-1960's, the whole system had become sufficiently sophisticated that it was possible for an engineer to set up a master tape and cutting lathe and just let it run, churning out master discs, stopping only to change the tape and put a fresh lacquer disc on the turntable. Al Kooper has described the Columbia Records mastering suites during this period--a series of cubicles in which the engineers would spend their time reading the newspaper while the lathes cut discs.

It should be no surprise that this lack of human involvement did not always produce artistically satisfactory results, and sometimes misguided human involvement actually made things worse. A striking example that I have heard was the initial Lp release of The Band's album "Cahoots". Whoever was responsible (there is no mastering credit on the album) decided that the album should be cut as "hot" as possible. They did this by feeding the master tape signal to disc at a radically elevated level. The limiters and compressors of the disc cutting system did their job, so the record can still be played; it just sounds consistently loud--no dynamic range to speak of aside from the fade-outs at the end of tunes--and absolutely lifeless, as the dynamics controllers sucked the life out of the sound. Plenty of other examples could be cited. In any case, it was not a tolerable situation for artists who cared about how their records sounded.


It was not long before a few enterprising engineers realized there might be a demand for record mastering done with care and skill, and so the independent mastering studio was born. Among the first was The Mastering Lab, started in Los Angeles in the late 1960's by engineer Doug Sax. Following in his footsteps were other engineers--Bob Ludwig and Bob Katz in New York City, Bernie Grundman in Los Angeles, Denny Purcell in Nashville, etc.

What they all had in common were really good ears, attention to detail, skill in setting up and using the best possible equipment, and devotion to customer satisfaction. When you brought work to one of these engineers, you could be confident, if your master tape was any good at all, that the resulting record would sound as good as, or even better than your tape. Word got around, and the work of the independent mastering engineers eventually influenced the entire industry, leading to a general upgrading of technical standards, even at the big, bottom-line oriented labels. It is because of the work of Doug Sax, Bob Ludwig and others that it became the normal practice to list the mastering engineer in the album credits. No longer was he or she just a faceless cog in record production. (The Band, after the disappointing results with "Cahoots", got Capitol Records to hire an independent mastering engineer for their next album, "Moondog Matinee". The credit on the album reads, "Mastering Engineer: (as always) Bob Ludwig, Sterling Sound.")


Mastering engineers are still with us but, for the most part, they no longer cut acetate master discs from analog open reel tapes. Indeed, due to the changes in record production caused by the CD, what such engineers now do is better described as pre-mastering. In this process, the recording is brought into final shape and recorded on digital media that is then sent to the CD pressing plant.

It may seem like this would be an easier process compared to the task facing the mastering engineer in the Lp era; the CD is an inherently more precise medium, without the mechanical quirks and limitations of analog disc recording. But the changes that have occurred in the industry as a whole have actually made the mastering stage of the record making process more complex.

Consider: in the days of the big record labels, each company would have staff engineers who would work to technical standards established by the company. There would be standards for calibrating tape recorders, level standards for all tapes recorded in the company studios, standard ways of interfacing equipment, etc. In some cases the record label engineers would actually have built much of the equipment that they were using.

Given this kind of controlled, organized environment, the tapes reaching the mastering suites could have a technical quality and consistency that would be predictable. The songs would already be in the order in which they would appear on the album, pauses between songs would be set by leader tape of the right length, levels would be pretty consistent, most equalization problems would have been dealt with, etc.

These days the sessions for a CD album could be recorded almost anywhere in the world, from large urban studios to somebody's bedroom studio. The engineer responsible for the final mixes could be anybody, including the artist. This way of working does open up artistic possibilities that may not have been available in the more regimented big record label system, but it also means that there is no longer the kind of technical oversight that the old system offered. For this reason, many mastering engineers now prefer that clients should not finish certain aspects of an album; that fade outs, spacing between songs, final levels for each song and other such matters be left for the mastering stage. They know from experience that clients who attempt to provide a really finished product will often botch the job because of inadequate skills or equipment. In today's fragmented, independent record business, technical competence cannot be taken for granted.


Regardless, many of us do it ourselves. Why not do your own pre-mastering? I am not saying you shouldn't. If you are confident in your ability as an engineer, especially when it comes to the details involved in assembling an album, if you have adequate equipment to produce CDRs that match up to commercial quality work, and if your priority is to save the money that a good mastering studio would cost you, by all means go ahead and roll your own. Just remember that the above includes several assumptions that might bear thinking about. To examine them one by one:

- Your ability as an engineer: doing a good job of pre-mastering a CD requires a peculiar set of knowledge and skills that are not necessarily required in other phases of engineering. Do you know how to adjust levels on a bunch of different tracks so that the listener is not constantly lunging for the volume control, while still ensuring that the CD is as loud as you want it to be and sounds as good as you want it to sound? Do you understand the compromises involved in equalizing already mixed program material as opposed to equalization used during mixdown? What playback levels should you be using? How should you calibrate your monitoring system? If questions like these make you scratch your head, maybe you should call a pro.
- Equipment: possibly most important is having really, really accurate monitoring loudspeakers, carefully calibrated, in a quiet, acoustically treated room. Otherwise, you just can't tell what you are doing. Your average recording studio control room (never mind what many people have at home) is just not good enough for truly professional CD pre-mastering--the speakers are usually not good enough, and the acoustics just aren't up to par. You can often do satisfactory mixes in such rooms, but attempting to do the final tweaking involved in mastering can become an exercise in compensating for imperfections in the listening environment.

Audio processing equipment is a more iffy area. We now have available excellent computer audio software, sometimes for surprisingly little money. You can get good results from a relatively modest computer workstation if you really know what you are doing. The same goes for much of the inexpensive analog and digital outboard gear available. Knowing when not to include a certain component in the signal chain can be really important. It all comes down to knowledge, and I think that is one of the best arguments for going to a pro. The fancy equipment a mastering studio may boast of doesn't hurt, but what you are really paying for is the skill of the engineer.

-Finally, what are your budget priorities? A typical middle range mastering house might charge $125 per hour. Mastering an entire album might take about a day. So, going to a pro might cost you about a thousand bucks. If you just finished putting together your first attempt at an album in your bedroom studio and you want to make copies for all your friends and relatives, the cost of professional mastering is probably out of line with your resources. But if you just spent months (or even years) on an album project, hired professional musicians to play on it and have hopes of commercial distribution, skimping on pre-mastering makes no sense at all. The money for professional mastering will be only a fraction of what you have already spent on the whole project, and having a top professional putting the final touches on your recording is far preferable to having someone with minimal qualifications (that might be--ahem--you) doing a less than satisfactory job. Between these two extremes there is, of course, a large gray area where you could go one way or the other, depending on intentions and budget.


Record mastering as a separate discipline started when tape recording was introduced to record production shortly after World War II. At first considered merely a technical stage of the record making process, the artistic impact of mastering on the final product came to be appreciated by artists and producers, which led to the rise of the independent mastering studio. The resources and skills of independent mastering engineers have since proven invaluable in this age of independent CD production. Today's mastering studio can serve as a final stage of technical and artistic quality control for almost any recorded project.

(1) Note: the quote is from page 107 of "Ring Resounding" by John Culshaw, Viking Press, NY, 1967. The book jacket quite rightly says it is "The stirring account of how Wagner's Der Ring des Nibelungen was recorded for the first time."


Since this article was first written, we have seen the rise of downloadable music, served up on iPods, iPhones and similar devices, usually in the form of MP3 files or similar compressed audio formats. It is logical to ask how this has changed the role of the mastering engineer, and if we even need him or her any longer.

My opinion is that the help of a qualified professional in putting the final touches on an album can still be very beneficial, even if many listeners will be purchasing it by downloading files from a web site. The same problems one faces with assembling an album on CD--obtaining consistent levels from track to track, achieving overall loudness similar to other recordings of the same musical genre, dealing with problems of tonal quality, etc., apply just as much to a playlist of MP3s as they do to a collection of tracks on a CD. It is a matter of technical quality control, of making sure that the end result meets the standard of professionalism that most listeners expect in commercial recorded product.

Of course there are some differences between CD production and downloadable music production, one such being the potential for "lossy" compressed file formats to degrade the sound quality. But even with this particular issue, you can be certain that the best mastering engineers have devoted time and energy investigating how the various file formats affect the sound, and how best to deal with any potential problems. My advice to the independent album producer remains the same--if you have a substantial investment in your record and want it to sound its best, there are real advantages in going to a top mastering engineer.

- Robert Auld, March, 2011.

Copyright 2011, Robert Auld

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