About Blue Mountain Mastering - What is the Mastering Process?

Not sure exactly what Audio Mastering is or does? Here is some useful information about Professional

Audio Mastering;

Mastering, a form of audio post-production, is the process of preparing and transferring recorded audio

from a source containing the final mix to a data storage device (the master); the source from which all copies

will be produced (via methods such as pressing, duplication or replication). The format of choice these days

is digital masters, although analog masters, such as audio tapes, are still being used by the manufacturing

industry and a few engineers who specialize in analog mastering.

Pre-1940s

In the earliest days of the recording industry, all phases of the recording and mastering process were entirely

achieved by mechanical processes. Performers sang and/or played into a large acoustic horn and the master

recording was created by the direct transfer of acoustic energy from the diaphragm of the recording horn

to the mastering lathe, which was typically located in an adjoining room. The cutting head, driven by the

energy transferred from the horn, inscribed a modulated groove into the surface of a rotating cylinder or disc.

These masters were usually made from either a soft metal alloy or from wax; this gave rise to the colloquial

term waxing, referring to the cutting of a record.

After the introduction of the microphone and electronic amplification in the late 1920s, the mastering process

became electro-mechanical, and electrically driven mastering lathes came into use for cutting master discs

(the cylinder format by then having been superseded).

However, until the introduction of tape recording, master recordings were almost always cut direct-to-disc.

Artists performed live in a specially designed studio and as the performance was underway, the signal was

routed from the microphones via a mixing desk in the studio control room to the mastering lathe, where the

disc was cut in real time.

Only a small minority of recordings were mastered using previously recorded material sourced from other

discs.

Advances

The recording industry was revolutionized by the introduction of magnetic tape in the late 1940s, which

enabled master discs to be cut separately in time and space from the actual recording process. Although

tape and other technical advances dramatically improved audio quality of commercial recordings in the

post-war years, the basic constraints of the electro-mechanical mastering process remained, and the

inherent physical limitations of the main commercial recording media—the 78 rpm disc and the later 7-inch

45 rpm single and the 33-1/3 rpm LP record—meant that the audio quality, dynamic range, and running

time of master discs were still relatively limited compared to later media such as the compact disc.

Running times were constrained by the diameter of the disc and the density with which grooves could be

inscribed on the surface without cutting into each other. Dynamic range was also limited by the fact that if

the signal level coming from the master tape was too high, the highly sensitive cutting head might jump off

the surface of the disc during the cutting process.

From the 1950s until the advent of digital recording in the late 1970s, the mastering process typically went

through several stages. Once the studio recording on multi-track tape was complete, a final mix was

prepared and dubbed down to the master tape, usually either a single-track mono or two-track stereo tape.

Prior to the cutting of the master disc, the master tape was often subjected to further electronic treatment by

a specialist mastering engineer. After the advent of tape it was found that, especially for pop recordings,

master recordings could be optimized by making fine adjustments to the balance and equalization prior to the

cutting of the master disc.

Mastering became a highly skilled craft and it was widely recognized that good mastering could make or

break a commercial pop recording. As a result, during the peak years of the pop music boom from the

1950s to the 1980s, the best mastering engineers were in high demand.

In large recording companies such as EMI, the mastering process was usually controlled by specialist staff

technicians who were conservative in their work practices. These big companies were often reluctant to make

changes to their recording and production processes—for example, EMI was very slow in taking up

innovations in multi-track recording and they did not install 8-track recorders in their Abbey Road Studios

until the late 1960s, more than a decade after the first commercial 8-track recorders were installed by

American independent studios. As a result, by the time The Beatles were making their groundbreaking

recordings in the mid-1960s, they often found themselves at odds with EMI's mastering engineers, who

were unwilling to meet the group's demands to push the mastering process because it was feared that if levels

were set too high it would cause the needle to jump out of the groove when the record was played by listeners.

Digital technology

In the 1990s, electro-mechanical processes were largely superseded by digital technology, with digital

recordings transferred to digital masters by an optical etching process that employs laser technology.

The digital audio workstation (DAW) became common in many mastering facilities, allowing the off-line

manipulation of recorded audio via a graphical user interface (GUI). Although many digital processing tools

are common during mastering, it is also very common to use analog media and processing equipment for

the mastering stage.

Just as in other areas of audio, the benefits and drawbacks of digital technology compared to analog

technology is still a matter of debate. However, in the field of audio mastering, the debate is usually over

the use of digital versus analog signal processing rather than the use of digital technology for storage of

audio.

Although in reality there isn't such a thing as an "optimum mix level for mastering", the example on this

picture to the right only suggests what mix levels are ideal for the studio engineer to render and for the

mastering engineer to process. It's very important to allow enough headroom for the mastering

engineer's work. Many mastering engineers working with digital equipment would agree that a minimum

of 3 to 6 dB of available headroom is critical to perform good mastering. Ideal peak levels should not

exceed -3dBFSD and the average sum of the left and right channels should be at around -10 to -18

dBFSD (As shown on the picture to the right).

There are mastering engineers who feel that digital technology, as of 2007, has not progressed enough

in quality to supersede analog technology entirely. Many top mastering studios, including Bernie Grundman

Mastering (which has mastered 37 Grammy-nominated albums), and Gateway Mastering, still embrace

analog signal processing (such as analog equalization) within the mastering process. Additionally, the latest

advances in analog mastering technology include 120V signal rails for previously unavailable headroom

of 150dB as well as frequency response ranging from 3 Hz to 300 kHz. In order to duplicate this frequency

response in digital domain, a sampling rate of at least 600 kHz would be required, by the Nyquist–Shannon

sampling theorem. However, it is pertinent that the extremes in this frequency range (3 Hz - 300 kHz),

are effectively inaudible, existing outside the range of most professional microphones.

The studio

The audio mastering studio is much different than a normal recording studio. In fact, keeping mastering

equipment, which consists of large consoles and monitoring devices, in a recording studio can actually

hinder the acoustics of a recording session. Arrangement of the equipment within the studio is also important

since the mastering engineer will want to be able to hear every detail of each track. By working with

a separate mastering engineer, the recording artist is also opened up to more creative opinions.

Process

The source material is processed using equalization, compression, limiting, noise reduction and other

processes. Subsequently, it is rendered to a medium such as CD or DVD. This mastered source material

is also put in the proper order at this stage. This is commonly called the assembly or track sequencing.

More tasks such as editing, pre-gapping, leveling, fading in and out, noise reduction and other signal

restoration and enhancement processes can be applied as part of the mastering stage.

The specific medium varies, depending on the intended release format of the final product. For digital

audio releases, there is more than one possible master medium, chosen based on replication factory

requirements or record label security concerns.

A mastering engineer may be required to take other steps, such as the creation of a PMCD

(Pre-Mastered Compact Disc), where this cohesive material needs to be transferred to a master

disc for mass replication. A good architecture of the PMCD is crucial for a successful transfer to

a glass master that will generate stampers for reproduction.

The process of audio mastering varies depending on the specific needs of the audio to be processed.

Steps of the process typically include but are not limited to the following:

1. Transferring the recorded audio tracks into the Digital Audio Workstation (DAW) (optional).
2. Sequence the separate songs or tracks (the spaces in between) as they will appear on the final

product (for example, an audio CD).
3. Process or "sweeten" audio to maximize the sound quality for its particular medium.
4. Transfer the audio to the final master format (i.e., Red Book-compatible audio CD or a CD-ROM

data, half-inch reel tape, PCM 1630 U-matic tape, etc.).

Examples of possible actions taken during mastering:

1. Edit minor flaws.
2. Apply noise reduction to eliminate hum and hiss.
3. Adjust stereo width.
4. Add ambience.
5. Equalize audio between tracks.
6. Adjust volumes.
7. Dynamic expansion.
8. Dynamic compression.
9. Peak limit the tracks.

The guidelines above are mainly descriptive of the mastering process and not considered specific

instructions applicable in a given situation. Mastering engineers need to examine the types of input

media, the expectations of the source producer or recipient, the limitations of the end medium and

process the subject accordingly. General rules of thumb can rarely be applied.

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