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{{Short description|Form of audio post-production}}
{{Mergefrom|Music mastering|date=March 2007}}
{{Unreferenced|date=August 2006}} {{Use American English|date=February 2020}}


] was commonly used to create master copies.]]
'''Mastering''' is the process of preparing and transferring recorded audio to a ] that will be used in the production of copies. The specific medium varies, depending on the intended release format of the final product. For ] releases, there is more than one possible master medium, chosen based on replication factory requirements and/or record label security concerns. The chosen medium is then used as the source from which all copies will be made (via methods such as pressing, duplication or ]).


'''Mastering''', a form of ], is the process of preparing and transferring recorded audio from a source containing the ] to a ] (the ]), the source from which all copies will be produced (via methods such as pressing, duplication or ]). In recent years, ]s have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering.<ref>{{cite web|url=https://thevinylfactory.com/features/analogue-digital-vinyl-mastering-interviews/ |title=What's actually going on when people talk about digital vs. analogue masters|date=18 October 2017 }}</ref>
==History==
===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 ] of the recording horn to the mastering ], 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 ] were usually made from either a soft metal alloy or from ]; this gave rise to the colloquial term "waxing", referring to the cutting of a record.


Mastering requires critical listening; however, software tools exist to facilitate the process. Results depend upon the intent of the engineer, their skills, the accuracy of the speaker monitors, and the listening environment. '''Mastering engineers''' often apply ] and ] in order to optimize sound translation on all playback systems.<ref name="mixmagazine" /> It is standard practice to make a copy of a master recording—known as a safety copy—in case the master is lost, damaged or stolen.
After the introduction of the ] and electronic ] 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).


==History==
However, until the introduction of tape recording, master recordings were almost always cut ]. Artists performed live in a specially-designed ] and as the performance was underway, the signal was routed from the microphones via a ] in the studio control room to the mastering lathe, where the disc was cut as the performance took place. Only a small minority of recordings were mastered using previously recorded material sourced from other discs.


===Advances=== ===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 or played into a large ] and the master recording was created by the direct transfer of acoustic energy from the ] of the recording horn to the ], 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.<ref name=Auld>{{cite magazine |url=http://www.recordingmag.com/resources/resourceDetail/109.html |title=Mastering Then and Now |author=Robert Auld |magazine=Recording |access-date=2016-01-19 |archive-url=https://web.archive.org/web/20171124115019/http://www.recordingmag.com/resources/resourceDetail/109.html |archive-date=2017-11-24 |url-status=dead }}</ref> These masters were usually made from either a soft metal alloy or from ]; this gave rise to the colloquial term ''waxing'', referring to the cutting of a record.<ref>{{citation |url=https://books.google.com/books?id=k_UDAAAAMBAJ&pg=PA47 |title=New Technique Aids LP Waxing |magazine=] |date=1950-03-25}}</ref>
The recording industry was revolutionised by the introduction of ] 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 78rpm disc and the later 7" single and ] -- meant that the audio quality, dynamic range and running time of master discs was still relatively limited compared to later media such as the ].


After the introduction of the ] and ] in the mid-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). Until the introduction of tape recording, master recordings were almost always cut ].<ref name=Auld/> Only a small minority of recordings were mastered using previously recorded material sourced from other discs.
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.


===Emergence of magnetic tape===
From the 1950s until the advent of digital recording in the late 1980s, the mastering process typically went through several stages. Once the studio recording on multitrack tape was complete, a final mix was prepared and dubbed down to the ] -- usually either a single-track ] or two-track ] tape.
In the late 1940s, the recording industry was revolutionized by the introduction of ]. Magnetic tape was invented for recording sound by ] in 1928 in Germany, based on the invention of ] by ] in 1898. Not until the end of ] could the technology be found outside Europe. The introduction of magnetic tape recording enabled master discs to be cut separately in time and space from the actual recording process.<ref name=Auld/>


Although tape and other technical advances dramatically improved the 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 later the 7-inch 45 rpm single and 33-1/3 rpm ]—meant that the audio quality, ],{{efn|Dynamic range was limited by the fact that if the mastering level was set too high, the cutting head might be damaged during the cutting process or the stylus may jump out of the groove during playback.<ref name=Auld/>}} and running time{{efn|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.}} of master discs were still limited compared to later media such as the ].
Prior to the cutting of the master disc, the master tape was often subjected to further electronic treatment by a specialist ]. After the advent of tape it was found that, especially for pop recordings, master recordings could be 'optimised' by making fine adjustments to the balance and equalisation prior to the cutting of the master disc.


===Electro-mechanical mastering process===
Mastering became a highly skilled craft and it was widely recognised that good mastering could make or break a commercial pop recording. As a result, during the peak years of the ] boom from the 1950s to the 1980s, the best mastering engineers were in high demand. In the 1970s and beyond, one of the most sought-after mastering engineers in the world was ]. The New York based engineer began his audio career at ] in New York as assistant to producer ] after which he spent many years based ], and then ], mastering recordings in all genres by artists from all over the world.
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 ] was prepared and dubbed down to the master tape, usually either a single-track ] or two-track ] 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 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 (]) prior to the cutting of the master disc.
Many artists found that their recordings were significantly degraded by sub-standard mastering, so some of the more technically adept pop musicians -- notably ] and ] -- learned this process and became highly skilled mastering engineers in their own right in addition to their musical accomplishments.


In large recording companies such as ], 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 ] and they did not install 8-track recorders in their ] 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 ] were making their groundbreaking recordings in the mid-Sixties, 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 consumers. In large recording companies such as ], 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 ]{{efn|In ] each signal input is recorded to its own track on a multi-track recorder. This multi-track tape is mixed down to a mono or stereo master tape. A multi-track tape may be remixed many times, in different ways, by different engineers, giving the possibility of several masters (mono version, stereo version, LP version, AM radio version, single version, etc.).}} and did not install 8-track recorders in their ] until the late 1960s, more than a decade after the first commercial 8-track recorders were installed by American independent studios.<ref>{{cite book|last1=Martin|first1=George|author-link1=George Martin|last2=Hornsby|first2=Jeremy|title=All you need is ears|year=1994|publisher=Macmillan|isbn=0-312-11482-6|page=143}}</ref>


===Digital technology=== ===Digital technology===
]
In the 1990s, the old electro-mechanical processes were largely superseded by digital technology, with digital recordings tranferred to digital masters by an optical etching process that employs ] technology. The ] (DAW) became common in many mastering facilities, allowing the off-line manipulation of recorded audio via a ] (GUI).
In the 1990s, electro-mechanical processes were largely superseded by digital technology, with ]s stored on ]s or digital tape and mastered to ]. The ] (DAW) became common in many mastering facilities, allowing the off-line manipulation of recorded audio via a ] (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 ] are still a matter for 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.<ref name="mixmagazine">{{cite magazine |url=http://mixonline.com/recording/mastering/audio_issues_modern_mastering |magazine=Mix Magazine |title=Issues in Modern Mastering |archive-url=https://web.archive.org/web/20070524113354/http://mixonline.com/recording/mastering/audio_issues_modern_mastering/ |archive-date=May 24, 2007 |date=May 1, 2006 |author=Blair Jackson}}</ref>

Digital systems have higher performance and allow mixing to be performed at lower maximum levels. When mixing to 24-bits with peaks between −3 and −10 dBFS on a mix, the mastering engineer has enough ] to process and produce a final master.<ref name="bob_katz"> {{webarchive |url=https://web.archive.org/web/20070827154625/http://www.digido.com/bob-katz/mixing-tips-and-tricks.html |date=August 27, 2007 }}</ref> Mastering engineers recommend leaving enough headroom on the mix to avoid distortion.<ref></ref> The reduction of dynamics by the mix or mastering engineer has resulted in a ] in commercial recordings.<ref name="Shelvock" />


== Process == == Process ==
]]]
The process of audio mastering varies depending on the specific needs of the audio to be processed.
The source material, ideally at the original ], is processed using ], ], ] and other processes. Additional operations, such as ], specifying the gaps between tracks, adjusting level, fading in and out, ] and other signal restoration and enhancement processes can also be applied as part of the mastering stage.<ref name="Shelvock">{{Cite book|title = Audio Mastering as Musical Practice|last = Shelvock|first = Matt|publisher = ETDR: University of Western Ontario|year = 2012|location = Ontario, Canada|pages = 1–72|url = http://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=1709&context=etd}}</ref> The source material is put in the proper order, commonly referred to as assembly (or 'track') sequencing. These operations prepare the music for either digital or analog, e.g. vinyl, replication.
Steps of the process typically include:
# Load the recorded audio tracks into the DAW.
# Correct any problems with the audio, such as volume level, tonal balance, or undesirable artifacts.
# Sequence the separate songs or tracks as it will appear on the final product (for example, a CD).
# Transfer the audio to the final master format (i.e., Redbook, CD-R, etc.).


If the material is destined for vinyl release, additional processing, such as dynamic range reduction or frequency-dependent stereo–to–mono fold-down and equalization may be applied to compensate for the limitations of that medium. For compact disc release, ''start of track'', ''end of track'', and ''indexes'' are defined for playback navigation along with ] (ISRC) and other information necessary to replicate a ]. Vinyl LP and ] have their own pre-duplication requirements for a finished master. Subsequently, it is rendered either to a physical medium, such as a CD-R or DVD-R, or to computer files, such as a ] (DDP) file set or an ]. Regardless of what delivery method is chosen, the replicator factory will transfer the audio to a ] that will generate metal stampers for replication.
Examples of possible actions taken during mastering:
# Apply ] to eliminate hum and hiss.
# ] the tracks to set the highest peaks in audio volume to a preset level; the overall audio should never exceed 0 ].
# Equalize audio between tracks to ensure there are no jumps in bass, treble, midrange, volume or pan.
# Apply a compressor (for example, 1.5:1 starting at -10 dB) to ] the peaks making the softer parts sound relatively louder.
# In the case of mastering for broadcast, the bandwidth of the signal has to be reduced. For example, for TV broadcast: apply a ] at 80 Hz with -18 dB/octave to filter out low frequencies and apply a ] at 12 kHz with -9 dB/octave to filter out high frequencies.
# In the case of CD or Vinyl or similar media, arrange the tracks in the desired order and make sure the pauses or crossfades between tracks are as they should be.


The guidelines above are not specific instructions but processes that may or may not be applied in a given situation. Mastering needs 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. The process of audio mastering varies depending on the specific needs of the audio to be processed. 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.


Steps of the process typically include the following:
== RMS in music, average loudness ==
# Transferring the recorded audio tracks into the ](DAW)
# Sequence the separate songs or tracks as they will appear on the final release
# Adjust the length of the silence between songs
# Process or ] audio to maximize the sound quality for the intended medium (e.g. applying specific EQ for vinyl)
# Transfer the audio to the final master format (CD-ROM, half-inch reel tape, ], etc.)


Examples of possible actions taken during mastering:<ref name="Shelvock" />
The ] (RMS) in audio production terminology is a measure of average level and is found widely in software tools. In practice, a larger RMS number means higher average level; i.e. -9 dBFSD RMS is 2 dB louder than -11 dBFSD RMS. The maximum value for the RMS number is therefore zero. The loudest records of modern music are -7 to -9 dBFSD RMS, the softest -12 to -16 dBFSD RMS. The RMS level is no absolute guarantee of loudness, however; perceived loudness of signals of similar RMS level can vary widely since perception of loudness is dependent on several factors, including the spectrum of the sound (see ]) and the density of the music (e.g., slow ballad versus fast rock).
# Editing minor flaws
# Applying ] to eliminate clicks, dropouts, hum and hiss
# Adjusting stereo width
# Equalize audio across tracks for the purpose of optimized frequency distribution
# Adjust volume
# Dynamic range compression or expansion
# ]
# Inserting ] codes and CD text
# Arranging tracks in their final sequential order
# Fading out the ending of each song
# ]


==Engineer==
== Compressed higher RMS vs clipped higher RMS, density ==
{{Multiple issues|section=yes|
{{Refimprove|section|date=October 2008}}
{{Original research|section|date=February 2022}}
}}
]s]]
A '''mastering engineer''' is a person skilled in the practice of taking ] (typically musical content) that has been previously mixed in either the ] or ] domain as mono, stereo, or multichannel formats and preparing it for use in ], whether by physical media such as a CD, vinyl record, or as some method of streaming audio.


===Education and experience===
Some experienced listeners feel that around -12 dBFSD RMS in general or during loud parts and -14 to -16 dBFSD RMS during soft parts is a "sweet spot" for optimal punch and loudness, neither too loud nor too soft. This perception is still valid considering that the extra loudness (usually 1-3 dB) has often been achieved by simply clipping the smoothly curved tops of the waveforms resulting in flat topped square waves, which may or may not result in a subjective improvement of the sound. Prior to clipping, usually the last procedure in audio production, the "natural" RMS of many songs is in fact just around -12 dBFSD RMS. Thus, in many cases where the final RMS is -8 to -11 dBFSD, the RMS has not really been increased over the -12 dBFSD RMS "sweet spot"; only the tops of the waveforms have been clipped by 1-3 dB. The music is not any thicker or denser, merely played louder with less punch and more distortion.
The mastering engineer is responsible for a final edit of a product and preparation for manufacturing copies. Although there are no official requirements to work as an audio mastering engineer, practitioners often have comprehensive domain knowledge of audio engineering, and in many cases, may hold an audio or acoustic engineering ]. Most ]s master music or speech audio material. The best mastering engineers might possess ] and production skills, allowing them to troubleshoot ] issues and improve the final sound. Generally, good mastering skills are based on experience, resulting from many years of practice.


===Equipment===
In contrast, a "true" higher RMS is achieved by increasing the density (usually by compression) of the sounds contributing most to the average level (i.e., everything but the drums), so that their volume as a group can be lower in relation to (usually drum) peaks. This retains the same RMS and perceived average loudness as the clipped mix, often with a stronger sense of density and pressure. However, in practice, this too would probably be subjected to some clipping, resulting in even higher loudness and pressure than one that was merely clipped.
Generally, mastering engineers use a combination of specialized audio-signal processors, low-distortion-high-bandwidth loudspeakers (and corresponding amplifiers with which to drive them), within a dedicated, acoustically-optimized playback environment. The equipment and processors used within the field of mastering are almost entirely dedicated to the purpose; engineered to a high standard, often possessing low signal-to-noise ratios and in many cases, the incorporation of parameter-recall, such as indented potentiometers, or in some more-sophisticated designs, via a digital-controller. Some advocates for digital software claim that plug-ins are capable of processing audio in a mastering context, though without the same degree of signal degradation as those introduced from processors within the analog domain. The quality of the results varies according to the algorithms used within these processors, which in some cases, can introduce distortions entirely exclusive to the digital domain.


]s, phase ]s, and also peak, RMS, VU and K meters are frequently used within the audio analysis stage of the process as a means of rendering a visual representation of the audio, or signal, being analyzed.
In summary, what is important is not how loud the song is made but ''how'' the song is made loud.


===Aspects of their work===
==Bit rate, sample rate, and dithering==
Most mastering engineer accolades are given for their ability to make a mix consistent with respect to subjective factors based on the perception of listeners, regardless of their playback systems and the environment. This is a difficult task due to the varieties of systems now available and the effect it has on the apparent qualitative attributes of the ]. For instance, a recording that sounds great on one ]/] combination playing CD audio, may sound drastically different on a computer-based system playing back a low-] ]. Some engineers maintain that the main mastering engineer's task is to improve upon playback systems translations while the position of others is to make a sonic impact.<ref name="edward_vinatea">{{cite web |url=http://musicmasteringonline.com/understanding-mastering/ |title=Understanding Mastering |last=Vinatea |first=Edward |date=24 April 2010 |website=The Directory of Mastering Studios |access-date=2 February 2018}}</ref>


Prolonged periods of listening to improperly mastered recordings usually leads to hearing fatigue that ultimately takes the pleasure out of the listening experience.<ref name="stylusmagazine"> {{cite magazine |last=Southall |first=Nick |date=1 May 2006 |title=Imperfect Sound Forever |url=http://www.stylusmagazine.com/articles/weekly_article/imperfect-sound-forever.htm |magazine=Stylus |archive-url=https://web.archive.org/web/20171203075701/http://www.stylusmagazine.com/articles/weekly_article/imperfect-sound-forever.htm |archive-date=3 December 2017 |access-date=2 February 2018 |url-status=dead}}</ref>
Since the onset of digital recording, another job of the mastering engineer is to make higher resolution recordings into ]. For example, professional digital audio is almost always recorded at 24 bits, whereas a CD quality is 16 bits. Similarly, some projects may be recorded at a higher ], such as 96kHz, whereas CD quality is 44.1kHz. While downsampling the audio is a relatively simple task, bit reduction has more blatant consequences. While reducing the ] from 24 bits to 16 bits, if one simply truncates the lower 8 bits it will lead to distortion and other subjectively ugly artifacts, called ]. The solution, or perhaps compromise, is to ] the signal. This process will add lower level ] instead of the distortion - a subjectively more pleasing sound. Some even believe proper dithering can make 16 bit audio sound as though it actually has the ] of 19 or 20 bit audio. Dithering noise can also be shaped in a way that makes it less audible by placing most of the noise in a higher frequency range, by principle of the ] curve. The sound is not dissimilar to ] noise. Different dithering processes have different sounds, and thus the mastering engineer will choose the dither that he believes to be most appropriate for the type of music.

== New trends ==

'''Artmastering''' is a process of mastering audio material with special emphasis on the artistic content of the music.

During the process of artmastering, an engineer together with the artist and his/her creative team focus on the artistic elements of an audio material, and try to devise a method, technique or process needed to accomplish the sonic goals by all means necessary whether subtle or radical.

As in traditional mastering, artmastering tries to achieve the best sonic quality of the material as defined by the artistic sense of human beings rather then by some rigid technical specifications such as frequency-response or signal-to-noise-ratio. During artmastering, an engineer has wider latitude and may either stay within the traditional boundaries of the mastering art or step beyond them according to the artist's wishes.

== Software tools for mastering ==
Digital Audio Workstations
{|
| style="vertical-align: top;" |
* ]
* Apple WaveBurner
* ]
* Audio Cube
* ]
* ]
* iZotope
* ]
* ]
* ]
| style="vertical-align: top;" |
* ]
* SaDiE
* Seqouia
* ]
* Sonic Studio
* Sony CD Architect
* Sony Sonoma
* ]
* WaveLab
* ]
|}


===Notable audio mastering engineers===
{{div col|colwidth=20em}}
*]
*]
*]
*]
*]
*]
*]
*]<ref>{{cite news |url=https://www.latimes.com/entertainment/music/la-et-ms-bernie-grundman-mastering-red-bull-20171022-story.html |last=Wood |first=Mikael |title=Bernie Grundman wants to change the way you hear music — for the better |work=Los Angeles Times |date=2017-10-27 |access-date=2020-01-26}}</ref>
*]<ref>{{cite magazine|url=https://tapeop.com/articles/85/steve-hoffman/ |last=Hanlon |first=Keith |title=Steve Hoffman: Mastering The Beach Boys, Miles Davis, & More |magazine=TapeOp Magazine |date=September–October 2011 |access-date=2020-01-26}}</ref>
*]
*]
*]
*]
*]
*]
*]<ref>{{cite news |url=https://www.hollywoodreporter.com/news/george-marino-legendary-mastering-engineer-333020 |last=Barnes |first=Mike |title=George Marino, Legendary Mastering Engineer, Dies |work=Hollywood Reporter |date=2012-06-04 |access-date=2020-01-26}}</ref>
*]
*]
*]
*]<ref>{{cite web|url=http://ericpillai.com/site/|title=Eric Pillai – Future Sound of Bombay}}</ref>
*]
*]
*]
*]
*]
*]
*]
{{div col end}}


== See also ==
* ]
* ]
* ]
* ]
* ]
* ]


==Notes==
{{Notelist}}


== References ==
{{Reflist}}


{{Music production}}
{{Authority control}}


{{DEFAULTSORT:Audio Mastering}}
] ]
] ]
]

]
]
]
]
]
]
]
]
]
]
]
]

Latest revision as of 16:10, 26 September 2024

Form of audio post-production

Magnetic tape was commonly used to create master copies.

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). In recent years, digital masters have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering.

Mastering requires critical listening; however, software tools exist to facilitate the process. Results depend upon the intent of the engineer, their skills, the accuracy of the speaker monitors, and the listening environment. Mastering engineers often apply equalization and dynamic range compression in order to optimize sound translation on all playback systems. It is standard practice to make a copy of a master recording—known as a safety copy—in case the master is lost, damaged or stolen.

History

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 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, 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 amplifier in the mid-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). Until the introduction of tape recording, master recordings were almost always cut direct-to-disc. Only a small minority of recordings were mastered using previously recorded material sourced from other discs.

Emergence of magnetic tape

In the late 1940s, the recording industry was revolutionized by the introduction of magnetic tape. Magnetic tape was invented for recording sound by Fritz Pfleumer in 1928 in Germany, based on the invention of magnetic wire recording by Valdemar Poulsen in 1898. Not until the end of World War II could the technology be found outside Europe. The introduction of magnetic tape recording enabled master discs to be cut separately in time and space from the actual recording process.

Although tape and other technical advances dramatically improved the 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 later the 7-inch 45 rpm single and 33-1/3 rpm LP record—meant that the audio quality, dynamic range, and running time of master discs were still limited compared to later media such as the compact disc.

Electro-mechanical mastering 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 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.

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 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.

Digital technology

Optimum Digital Levels with respect to the Full Digital Scale (dBFSD)

In the 1990s, electro-mechanical processes were largely superseded by digital technology, with digital recordings stored on hard disk drives or digital tape and mastered to CD. 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 are still a matter for 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.

Digital systems have higher performance and allow mixing to be performed at lower maximum levels. When mixing to 24-bits with peaks between −3 and −10 dBFS on a mix, the mastering engineer has enough headroom to process and produce a final master. Mastering engineers recommend leaving enough headroom on the mix to avoid distortion. The reduction of dynamics by the mix or mastering engineer has resulted in a loudness war in commercial recordings.

Process

A common mastering processor for dynamic range compression

The source material, ideally at the original resolution, is processed using equalization, compression, limiting and other processes. Additional operations, such as editing, specifying the gaps between tracks, adjusting level, fading in and out, noise reduction and other signal restoration and enhancement processes can also be applied as part of the mastering stage. The source material is put in the proper order, commonly referred to as assembly (or 'track') sequencing. These operations prepare the music for either digital or analog, e.g. vinyl, replication.

If the material is destined for vinyl release, additional processing, such as dynamic range reduction or frequency-dependent stereo–to–mono fold-down and equalization may be applied to compensate for the limitations of that medium. For compact disc release, start of track, end of track, and indexes are defined for playback navigation along with International Standard Recording Code (ISRC) and other information necessary to replicate a CD. Vinyl LP and cassettes have their own pre-duplication requirements for a finished master. Subsequently, it is rendered either to a physical medium, such as a CD-R or DVD-R, or to computer files, such as a Disc Description Protocol (DDP) file set or an ISO image. Regardless of what delivery method is chosen, the replicator factory will transfer the audio to a glass master that will generate metal stampers for replication.

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

Steps of the process typically include the following:

  1. Transferring the recorded audio tracks into the Digital Audio Workstation (DAW)
  2. Sequence the separate songs or tracks as they will appear on the final release
  3. Adjust the length of the silence between songs
  4. Process or sweeten audio to maximize the sound quality for the intended medium (e.g. applying specific EQ for vinyl)
  5. Transfer the audio to the final master format (CD-ROM, half-inch reel tape, PCM 1630 U-matic tape, etc.)

Examples of possible actions taken during mastering:

  1. Editing minor flaws
  2. Applying noise reduction to eliminate clicks, dropouts, hum and hiss
  3. Adjusting stereo width
  4. Equalize audio across tracks for the purpose of optimized frequency distribution
  5. Adjust volume
  6. Dynamic range compression or expansion
  7. Peak limit
  8. Inserting ISRC codes and CD text
  9. Arranging tracks in their final sequential order
  10. Fading out the ending of each song
  11. Dither

Engineer

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Mastering engineer Doug Sax with four disc cutting lathes

A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analogue 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 streaming audio.

Education and experience

The mastering engineer is responsible for a final edit of a product and preparation for manufacturing copies. Although there are no official requirements to work as an audio mastering engineer, practitioners often have comprehensive domain knowledge of audio engineering, and in many cases, may hold an audio or acoustic engineering degree. Most audio engineers master music or speech audio material. The best mastering engineers might possess arrangement and production skills, allowing them to troubleshoot mix issues and improve the final sound. Generally, good mastering skills are based on experience, resulting from many years of practice.

Equipment

Generally, mastering engineers use a combination of specialized audio-signal processors, low-distortion-high-bandwidth loudspeakers (and corresponding amplifiers with which to drive them), within a dedicated, acoustically-optimized playback environment. The equipment and processors used within the field of mastering are almost entirely dedicated to the purpose; engineered to a high standard, often possessing low signal-to-noise ratios and in many cases, the incorporation of parameter-recall, such as indented potentiometers, or in some more-sophisticated designs, via a digital-controller. Some advocates for digital software claim that plug-ins are capable of processing audio in a mastering context, though without the same degree of signal degradation as those introduced from processors within the analog domain. The quality of the results varies according to the algorithms used within these processors, which in some cases, can introduce distortions entirely exclusive to the digital domain.

Real-time analyzers, phase oscilloscopes, and also peak, RMS, VU and K meters are frequently used within the audio analysis stage of the process as a means of rendering a visual representation of the audio, or signal, being analyzed.

Aspects of their work

Most mastering engineer accolades are given for their ability to make a mix consistent with respect to subjective factors based on the perception of listeners, regardless of their playback systems and the environment. This is a difficult task due to the varieties of systems now available and the effect it has on the apparent qualitative attributes of the recording. For instance, a recording that sounds great on one speaker/amplifier combination playing CD audio, may sound drastically different on a computer-based system playing back a low-bitrate MP3. Some engineers maintain that the main mastering engineer's task is to improve upon playback systems translations while the position of others is to make a sonic impact.

Prolonged periods of listening to improperly mastered recordings usually leads to hearing fatigue that ultimately takes the pleasure out of the listening experience.

Notable audio mastering engineers

See also

Notes

  1. Dynamic range was limited by the fact that if the mastering level was set too high, the cutting head might be damaged during the cutting process or the stylus may jump out of the groove during playback.
  2. 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.
  3. In multi-track recording each signal input is recorded to its own track on a multi-track recorder. This multi-track tape is mixed down to a mono or stereo master tape. A multi-track tape may be remixed many times, in different ways, by different engineers, giving the possibility of several masters (mono version, stereo version, LP version, AM radio version, single version, etc.).

References

  1. "What's actually going on when people talk about digital vs. analogue masters". 18 October 2017.
  2. ^ Blair Jackson (May 1, 2006). "Issues in Modern Mastering". Mix Magazine. Archived from the original on May 24, 2007.
  3. ^ Robert Auld. "Mastering Then and Now". Recording. Archived from the original on 2017-11-24. Retrieved 2016-01-19.
  4. "New Technique Aids LP Waxing", Billboard, 1950-03-25
  5. Martin, George; Hornsby, Jeremy (1994). All you need is ears. Macmillan. p. 143. ISBN 0-312-11482-6.
  6. Bob Katz Mixing Tips Archived August 27, 2007, at the Wayback Machine
  7. How much headroom for mastering?
  8. ^ Shelvock, Matt (2012). Audio Mastering as Musical Practice. Ontario, Canada: ETDR: University of Western Ontario. pp. 1–72.
  9. Vinatea, Edward (24 April 2010). "Understanding Mastering". The Directory of Mastering Studios. Retrieved 2 February 2018.
  10. Southall, Nick (1 May 2006). "Imperfect Sound Forever". Stylus. Archived from the original on 3 December 2017. Retrieved 2 February 2018.
  11. Wood, Mikael (2017-10-27). "Bernie Grundman wants to change the way you hear music — for the better". Los Angeles Times. Retrieved 2020-01-26.
  12. Hanlon, Keith (September–October 2011). "Steve Hoffman: Mastering The Beach Boys, Miles Davis, & More". TapeOp Magazine. Retrieved 2020-01-26.
  13. Barnes, Mike (2012-06-04). "George Marino, Legendary Mastering Engineer, Dies". Hollywood Reporter. Retrieved 2020-01-26.
  14. "Eric Pillai – Future Sound of Bombay".
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