Mastering, a form of audio
post-productionPost-production is part of the filmmaking process. It occurs in the making of motion pictures, television programs, radio programs, videos, audio recordings, photography and digital art...
, is the process of preparing and transferring recorded audio from a source containing the final mix to a
data storage devicethumb|200px|right|A reel-to-reel tape recorder .The magnetic tape is a data storage medium. The recorder is data storage equipment using a portable medium to store the data....
(the
master); the source from which all copies will be produced (via methods such as pressing, duplication or
replicationIn optical disc manufacturing, replication is the process of producing discs via methods that do not involve "burning" blank CD, DVD or other discs; the latter is known as duplication.The replication of optical discs involves:...
). 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 have specialized themselves 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
diaphragmIn a loudspeaker, a diaphragm is the thin, semi-rigid membrane attached to the voice coil, which moves in a magnetic gap, vibrating the diaphragm, and producing sound...
of the recording horn to the mastering
latheA lathe is a machine tool which spins a block of material to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.Lathes are used in woodturning,...
, 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
mastersA master recording is an original recording, from which copies may be made.When recording on to magnetic or digital tape, the original tape is known as the master tape.When recording on to a computer hard disk, it is known as session files....
were usually made from either a soft metal alloy or from
waxWax refers to beeswax or another substance with similar properties. The traditional meaning, beeswax, refers to a substance secreted by bees and used by them in constructing their honeycombs...
; this gave rise to the colloquial term
waxing, referring to the cutting of a record.
After the introduction of the
microphoneA microphone, colloquially called a mic or mike , is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1876, Emile Berliner invented the first microphone used as a telephone voice transmitter...
and electronic
amplificationAmplification may refer to:* The operation of an amplifier, a natural or artificial device intended to make a signal stronger.* See also Fluidic Amplifier* Amplification , a figure of speech that adds importance to increase its rhetorical effect...
in the mid-1920s, the mastering process became electro-mechanical, and electrically driven mastering
latheA lathe is a machine tool which spins a block of material to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.Lathes are used in woodturning,...
s 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-discDirect to disc recording refers to sound recording methods which bypass the use of magnetic recording tape, recording directly onto disc master; and record albums made using this process....
. 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 tapeMagnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic. Nearly all recording tape is of this type, whether used for recording audio or video or for computer data storage. It was originally developed in Germany,...
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 recordA gramophone record, commonly known as phonograph record, vinyl record, or simply record, is an analog sound storage medium consisting of a flat disc with an inscribed modulated spiral groove usually starting near the periphery and ending near the centre of the disc...
—meant that the audio quality,
dynamic rangeDynamic range is a term used frequently in numerous fields to describe the ratio between the smallest and largest possible values of a changeable quantity, such as in sound and light...
, and running time of master discs were still relatively limited compared to later media such as the
compact discA Compact Disc is an optical disc used to store digital data. It was originally developed to store sound recordings exclusively, but later it also allowed the preservation of other types of data. Audio CDs have been commercially available since October 1982...
.
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
mixAudio mixing is the process by which a multitude of recorded sounds are combined into one or more channels, most commonly two-channel stereo. In the process, the source signals' level, frequency content, dynamics and panoramic position are commonly being manipulated and effects such as reverb might...
was prepared and dubbed down to the
master tapeA master recording is an original recording, from which copies may be made.When recording on to magnetic or digital tape, the original tape is known as the master tape.When recording on to a computer hard disk, it is known as session files....
, usually either a single-track
monoMonaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
or two-track
stereoSTEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to pull respectively further ahead of and fall gradually behind the earth...
tape.
Prior to the cutting of the master disc, the master tape was often subjected to further electronic treatment by a specialist
mastering engineerA mastering engineer is one skilled in the practice of taking audio that has been previously mixed in either the analog or digital domain as mono, stereo, or multichannel formats and preparing it for use in distribution, whether by physical media such as a CD, vinyl record, or as some method of...
. After the advent of tape it was found that especially for pop recordings, master recordings could be made so that the resulting record would sound better. This was done by making fine adjustments to the amplitude of sound at different frequency bands (equalization) prior to the cutting of the master disc.
Record mastering became a highly prized and 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 musicPop music is a music genre that developed from the mid-1950s as a softer alternative to rock 'n' roll and later to rock music. It has a focus on commercial recording, often orientated towards a youth market, usually through the medium of relatively short and simple love songs...
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 StudiosAbbey Road Studios, established in November of 1931 by EMI in London, England, is an iconic recording studio located at Abbey Road, in St John's Wood in the City of Westminster...
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 BeatlesThe Beatles were an English rock band formed in Liverpool in 1960 who became one of the most commercially successful and critically acclaimed bands in the history of popular music...
were making their groundbreaking recordings in the mid-1960s, they often found themselves at odds with EMI's
mastering engineerA mastering engineer is one skilled in the practice of taking audio that has been previously mixed in either the analog or digital domain as mono, stereo, or multichannel formats and preparing it for use in distribution, whether by physical media such as a CD, vinyl record, or as some method of...
s, 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
laserA laser is a device that emits light through a process called stimulated emission. Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses...
technology. The
digital audio workstationA digital audio workstation is an electronic system designed to record, edit and play back digital audio. A key feature of DAWs is the ability to freely manipulate recorded sounds...
(DAW) became common in many mastering facilities, allowing the off-line manipulation of recorded audio via a
graphical user interfaceA graphical user interface is a type of user interface item that allows people to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 Players, Portable Media Players or Gaming devices; household appliances and office equipment with images rather than...
(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-Biography:He is most known for his mastering work and his studio, Bernie Grundman Mastering, which he opened in 1983 in Hollywood. The studio, which includes engineers Chris Bellman and Brian Gardner, mastered 37 projects which received Grammy Award nominations in 2005.Grundman and his studio have...
Mastering (which has mastered 37 Grammy-nominated albums), and
Gateway MasteringBob Ludwig is an American mastering engineer.He is a well known and respected figure within the music industry. Ludwig's craftsmanship is appreciated widely within the music profession, as testified by his extensive credits and demand for his work...
, still embrace
analog signal processingAnalog signal processing is any signal processing conducted on analog signals by analog means. "Analog" indicates something that is mathematically represented as a set of continuous values. This differs from "digital" which uses a series of discrete quantities to represent signal...
(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 theoremThe Nyquist–Shannon sampling theorem is a fundamental result in the field of information theory, in particular telecommunications and signal processing. Sampling is the process of converting a signal into a numeric sequence...
. However, it is pertinent that the extremes in this frequency range (3 Hz - 300 kHz), are effectively inaudible, existing outside the range of both the human ear and most professional microphones.
The studio
The music mastering studio is very different from a normal audio
recording studioA recording studio is a facility for sound recording. Ideally, the space is specially designed by an acoustician to achieve the desired acoustic properties...
. In fact, all the equipment and gear found in most recording and mixing studios can actually hinder the acoustics of a room to accurately monitor sound. Thus, the correct room acoustics and arrangement of the equipment inside a mastering studio is an important factor since the mastering engineer (ME) needs to hear in detail each mix. This room design should be non-environmental or with a minimum room interference. By working with an experienced mastering engineer, the recording artist is also open to more creative opinions and technical advice.
Process
The source material is processed using
equalizationEqualization, equalisation or EQ is the process of using passive or active electronic elements or digital algorithms for the purpose of altering the frequency response characteristics of a system....
, 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 audioDigital audio uses digital signals for sound reproduction. This includes analog-to-digital conversion, digital-to-analog conversion, storage, and transmission. In effect, the system commonly referred to as digital is in fact a discrete-time, discrete-level analog of a previous electrical analog...
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
PMCDPMCD is a specially formatted, recordable Compact Disc designed to be sent to a CD pressing plant for replication. The PreMaster CD format, developed in the early 1990s by the CD-ROM division of Sony, in cooperation with of Tokyo and Sonic Solutions, contained a hidden “PreMaster Cue Sheet” that...
(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:
- Transferring the recorded audio tracks into the Digital Audio Workstation (DAW) (optional).
- Sequence the separate songs or tracks (the spaces in between) as they will appear on the final product (for example, an audio CD).
- Process or "sweeten" audio to maximize the sound quality for its particular medium.
- 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:
- Edit minor flaws.
- Apply noise reduction to eliminate hum and hiss.
- Adjust stereo width.
- Add ambience.
- Equalize audio between tracks.
- Adjust volumes.
- Dynamic expansion.
- Dynamic compression.
- Peak limit
In electronics, a limiter is a circuit that allows signals below a specified input power to pass unaffected while attenuating the peaks of stronger signals that exceed this input power....
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.
Audio mastering tools (hardware)
Audio consoles
Monitors
Master recorders
DAW
Converters & Encorders
Digital Signal Processors
- TC Electronic System 6000
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Equalizers
Dynamics
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Audio mastering tools (software)
- FL Studio
FL Studio, formerly known as FruityLoops, is a digital audio workstation developed by Belgian company Image-Line Software. FL Studio was originally the creation of Didier Dambrin, who is now the lead programmer at Image-Line responsible for its core development.FL Studio features a fully...
- Audacity
Audacity is a digital audio editor and recording application. Audacity is cross-platform and is available for Windows, Mac OS X, Linux and BSD.Audacity was created by Dominic Mazzoni while a graduate student at Carnegie Mellon University...
- WaveBurner Pro
WaveBurner is a Mac OS X professional application bundled with Logic Studio for assembling, mastering, and burning audio CDs. Audio CDs created with WaveBurner can be played back on any audio CD player, and can be used as premasters to produce CDs in large numbers for possible...
- Ardour
Ardour is a hard disk recorder and digital audio workstation application. It runs on Linux, Mac OS X and FreeBSD. Its primary author is Paul Davis, who is also responsible for the JACK Audio Connection Kit...
- BIAS Peak
Peak is a full-featured consumer stereo sample editor for the Macintosh computing platform. Peak is BIAS’ flagship product, and over the years, has been available in a number of different editions with varying levels of features....
- Cakewalk Sonar
Cakewalk SONAR is a computer program made by Cakewalk for recording, editing, mixing, mastering and outputting audio. The latest versions of the software are SONAR Home Studio 7, SONAR Home Studio 7 XL, SONAR 8.5 Studio Edition, SONAR 8.5 Producer Edition, and SONAR LE...
- Cubase
- Digital Performer
Digital Performer is a full-featured Digital Audio Workstation/Sequencer software package published by Mark of the Unicorn of Cambridge, Massachusetts for the Apple Macintosh platform.-Ancestry:...
- Ableton Live
Ableton Live is a professional loop-based software music sequencer for Mac OS and Windows by Ableton. The latest major release of Live, Version 8, was released in April 2009. Unlike other software sequencers, Live is designed around the notion of being as much an instrument for live performances as...
- Adobe Audition
Adobe Audition is a digital audio editor computer program from Adobe Systems featuring both a multitrack, non-destructive mix/edit environment and a destructive-approach waveform editing view.-Origins:...
- iZotope
iZotope, Inc. is an audio technology company based in Cambridge, Massachusetts, United States. iZotope develops professional audio software for audio recording, mixing, broadcast, sound design, and mastering which can be used in Digital Audio Workstation programs including Pro Tools, Apple Logic...
Ozone |
Jamin
Logic ProLogic Pro is a digital audio workstation and MIDI sequencer software application for the Mac OS X platform. Originally created by German software developer Emagic, Logic Pro became an Apple product when Apple bought Emagic in 2002...
NuendoNuendo is a digital audio workstation developed by Steinberg. The package is aimed at multimedia production, but is frequently used for audio post-production.- See also :* Comparison of multitrack recording software* Ableton Live* ACID Pro...
Pro ToolsPro Tools is a Digital Audio Workstation platform for Mac OS X and Microsoft Windows operating systems, developed and manufactured by Digidesign, a division of Avid Technology. It is widely used by professionals throughout the audio industries for recording and editing in music production, film...
SADiESadie, a black Labrador Retriever, is a 2007 recipient of the Dickin Medal . She was awarded the medal for finding a bomb planted underneath sandbags, close to where a German soldier was killed by a suicide car bombing outside the United Nations headquarters in Kabul in November 2005...
Samplitude
Sequoia
Sound ForgeSony Sound Forge is a digital audio editing suite by Sony Creative Software which is aimed at the professional and semi-professional markets....
SteinbergSteinberg is a German musical software and equipment company based in Hamburg. It mainly produces MIDI music sequencer software, software synthesizers and digital audio editing tools.- History :...
WaveLabWaveLab is a digital audio editor by Steinberg aimed at the professional as well as the semi-professional market. It supports multi-channel files, DirectX plugin, VST plugin and DVD-Audio creation. WaveLab was for a long time the main competitor to Sound Forge. Wavelab was started in 1995 and it is...
5 & 6
DigidesignDigidesign is an American digital audio technology company. It was founded in 1984 by Peter Gotcher and Evan Brooks. The company began as a project to raise money for the founders' band, selling EPROM chips for drum machines...
- Masterlist CD (Discontinued)
Universal AudioUniversal Audio is the fifth and final studio album by Scottish indie rock band The Delgados, released September 20 2004. The album is considered to showcase a more 'stripped down' sound than its predecessor Hate, featuring less orchestral themes....
UAD Precision Mastering Bundle, 1073 Equalizer
Finis 3 - Three band peak limiter. |
SONAR
See also
- Audio post production
Audio post production is the general term for all stages of production happening between the actual recording in a studio and the completion of a master recording. It involves, sound design, sound editing, audio mixing, and the addition of effects.- Film :...
- Full Scale Digital
- Loudness war
The loudness war is the music industry's tendency to record, produce, and broadcast music at progressively increasing levels of loudness to attempt to create a sound that stands out from others....
- Mastering engineer
A mastering engineer is one skilled in the practice of taking audio that has been previously mixed in either the analog or digital domain as mono, stereo, or multichannel formats and preparing it for use in distribution, whether by physical media such as a CD, vinyl record, or as some method of...
- Master recording
A master recording is an original recording, from which copies may be made.When recording on to magnetic or digital tape, the original tape is known as the master tape.When recording on to a computer hard disk, it is known as session files....
- Needle drop
A Needle drop is a common term used to describe a version of a music album that has been transferred from a vinyl record to digital audio or other formats...