Mastering (audio)

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Magnetic tape was commonly used to create master copies. Reel-to-ReelTapeBigHub.agr.jpg
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. [1]

Contents

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. [2] 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. [3] 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. [4]

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electrically driven mastering lathes came into use for cutting master discs (the cylinder format by then having been superseded).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. [3] 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. [3]

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, [lower-alpha 1] and running time [lower-alpha 2] 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 [lower-alpha 3] 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. [5]

Digital technology

Optimum Digital Levels with respect to the Full Digital Scale (dBFSD) Optimum-mix-levels-for-mast.jpg
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. [2]

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. [6] Mastering engineers recommend leaving enough headroom on the mix to avoid distortion. [7] The reduction of dynamics by the mix or mastering engineer has resulted in a loudness war in commercial recordings. [8]

Process

A common mastering processor for dynamic range compression Manleyvarimu.jpg
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. [8] 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: [8]

  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

Mastering engineer Doug Sax with four disc cutting lathes Doug Sax with 4 Lathes.jpg
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 [at nominal operating levels] 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. [9]

Prolonged periods of listening to improperly mastered recordings usually leads to hearing fatigue that ultimately takes the pleasure out of the listening experience. [10]

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. [3]
  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.).

Related Research Articles

Sound can be recorded and stored and played using either digital or analog techniques. Both techniques introduce errors and distortions in the sound, and these methods can be systematically compared. Musicians and listeners have argued over the superiority of digital versus analog sound recordings. Arguments for analog systems include the absence of fundamental error mechanisms which are present in digital audio systems, including aliasing and associated anti-aliasing filter implementation, jitter and quantization noise. Advocates of digital point to the high levels of performance possible with digital audio, including excellent linearity in the audible band and low levels of noise and distortion.

<span class="mw-page-title-main">Mixing console</span> Device used for audio mixing

A mixing console or mixing desk is an electronic device for mixing audio signals, used in sound recording and reproduction and sound reinforcement systems. Inputs to the console include microphones, signals from electric or electronic instruments, or recorded sounds. Mixers may control analog or digital signals. The modified signals are summed to produce the combined output signals, which can then be broadcast, amplified through a sound reinforcement system or recorded.

<span class="mw-page-title-main">Quadraphonic sound</span> Four-channel speaker audio

Quadraphonic sound – equivalent to what is now called 4.0 surround sound – uses four audio channels in which speakers are positioned at the four corners of a listening space. The system allows for the reproduction of sound signals that are independent of one another.

<span class="mw-page-title-main">Multitrack recording</span> Separate recording of multiple sound sources to create a cohesive whole

Multitrack recording (MTR), also known as multitracking, is a method of sound recording developed in 1955 that allows for the separate recording of multiple sound sources or of sound sources recorded at different times to create a cohesive whole. Multitracking became possible in the mid-1950s when the idea of simultaneously recording different audio channels to separate discrete tracks on the same reel-to-reel tape was developed. A track was simply a different channel recorded to its own discrete area on the tape whereby their relative sequence of recorded events would be preserved, and playback would be simultaneous or synchronized.

<span class="mw-page-title-main">Reel-to-reel audio tape recording</span> Audio recording using magnetic tape spooled on open reels

Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the supply reel containing the tape is placed on a spindle or hub. The end of the tape is manually pulled from the reel, threaded through mechanical guides and over a tape head assembly, and attached by friction to the hub of the second, initially empty takeup reel. Reel-to-reel systems use tape that is 1⁄4, 1⁄2, 1, or 2 inches wide, which normally moves at 3+3⁄4, 7+1⁄2, 15 or 30 inches per second. Domestic consumer machines almost always used 1⁄4 inch (6.35 mm) or narrower tape and many offered slower speeds such as 1+7⁄8 inches per second (4.762 cm/s). All standard tape speeds are derived as a binary submultiple of 30 inches per second.

<span class="mw-page-title-main">Monaural sound</span> Sound intended to be heard as if it were emanating from one position

Monaural sound or monophonic sound is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or stereo, which uses two separate audio channels to reproduce sound from two microphones on the right and left side, which is reproduced with two separate loudspeakers to give a sense of the direction of sound sources. In mono, only one loudspeaker is necessary, but, when played through multiple loudspeakers or headphones, identical audio signals are fed to each speaker, resulting in the perception of one-channel sound "imaging" in one sonic space between the speakers. Monaural recordings, like stereo ones, typically use multiple microphones fed into multiple channels on a recording console, but each channel is "panned" to the center. In the final stage, the various center-panned signal paths are usually mixed down to two identical tracks, which, because they are identical, are perceived upon playback as representing a single unified signal at a single place in the soundstage. In some cases, multitrack sources are mixed to a one-track tape, thus becoming one signal. In the mastering stage, particularly in the days of mono records, the one- or two-track mono master tape was then transferred to a one-track lathe used to produce a master disc intended to be used in the pressing of a monophonic record. Today, however, monaural recordings are usually mastered to be played on stereo and multi-track formats, yet retain their center-panned mono soundstage characteristics.

dbx (noise reduction) Family of noise reduction systems

dbx is a family of noise reduction systems developed by the company of the same name. The most common implementations are dbx Type I and dbx Type II for analog tape recording and, less commonly, vinyl LPs. A separate implementation, known as dbx-TV, is part of the MTS system used to provide stereo sound to North American and certain other TV systems. The company, dbx, Inc., was also involved with Dynamic Noise Reduction (DNR) systems.

<span class="mw-page-title-main">Digital audio workstation</span> Electronic device or application software used for recording, editing and producing audio files

A digital audio workstation is an electronic device or application software used for recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software program on a laptop, to an integrated stand-alone unit, all the way to a highly complex configuration of numerous components controlled by a central computer. Regardless of configuration, modern DAWs have a central interface that allows the user to alter and mix multiple recordings and tracks into a final produced piece.

<span class="mw-page-title-main">Dolby</span> Audio technology company

Dolby Laboratories, Inc. is a British-American technology corporation specializing in audio noise reduction, audio encoding/compression, spatial audio, and HDR imaging. Dolby licenses its technologies to consumer electronics manufacturers.

<span class="mw-page-title-main">Digital recording</span> Audio or video represented as a stream of discrete numbers

In digital recording, an audio or video signal is converted into a stream of discrete numbers representing the changes over time in air pressure for audio, or chroma and luminance values for video. This number stream is saved to a storage device. To play back a digital recording, the numbers are retrieved and converted back into their original analog audio or video forms so that they can be heard or seen.

A remaster is a change in the sound or image quality of previously created forms of media, whether audiophonic, cinematic, or videographic. The resulting product is said to be remastered. The terms digital remastering and digitally remastered are also used.

<span class="mw-page-title-main">Stereophonic sound</span> Method of sound reproduction using two audio channels

Stereophonic sound, or more commonly stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configuration of two loudspeakers in such a way as to create the impression of sound heard from various directions, as in natural hearing.

<span class="mw-page-title-main">Sound recording and reproduction</span> Recording of sound and playing it back

Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording.

Soundstream Inc. was the first United States audiophile digital audio recording company, providing commercial services for recording and computer-based editing.

The history of sound recording - which has progressed in waves, driven by the invention and commercial introduction of new technologies — can be roughly divided into four main periods:

The dbx Model 700 Digital Audio Processor was a professional audio ADC/DAC combination unit, which digitized a stereo analog audio input into a bitstream, which was then encoded and encapsulated in an analog composite video signal, for recording to tape using a VCR as a transport. Unlike other similar pieces of equipment like the Sony PCM-F1, the Model 700 used a technique called Companded Predictive Delta Modulation, rather than the now-common pulse-code modulation. At the time of its introduction in the mid-1980s the device was the first commercial product to use this method, although it had been proposed in the 1960s and prototyped in the late '70s.

Record restoration, a particular kind of audio restoration, is the process of converting the analog signal stored on gramophone records into digital audio files that can then be edited with computer software and eventually stored on a hard-drive, recorded to digital tape, or burned to a CD or DVD. The process may be divided into several separate steps performed in the following order:

  1. Cleaning the record, to prevent unwanted audio artifacts from being introduced in the capture that will necessitate correction in the digital domain, and to prevent unnecessary wear and damage to the stylus used in playback.
  2. Transcription of the record to another format on another medium ;
  3. Processing the raw sound file with software in order to remove transient noise resulting from record surface damage ;
  4. Using software to adjust the volume and equalization;
  5. Processing the audio with digital and analogue techniques to reduce surface/wideband noise;
  6. Saving the file in the desired format.
<span class="mw-page-title-main">History of multitrack recording</span>

Multitrack recording of sound is the process in which sound and other electro-acoustic signals are captured on a recording medium such as magnetic tape, which is divided into two or more audio tracks that run parallel with each other. Because they are carried on the same medium, the tracks stay in perfect synchronization, while allowing multiple sound sources to be recorded at different times.

<span class="mw-page-title-main">Audio mixing (recorded music)</span> Audio mixing to yield recorded sound

In sound recording and reproduction, audio mixing is the process of optimizing and combining multitrack recordings into a final mono, stereo or surround sound product. In the process of combining the separate tracks, their relative levels are adjusted and balanced and various processes such as equalization and compression are commonly applied to individual tracks, groups of tracks, and the overall mix. In stereo and surround sound mixing, the placement of the tracks within the stereo field are adjusted and balanced. Audio mixing techniques and approaches vary widely and have a significant influence on the final product.

A mixing engineer is responsible for combining ("mixing") different sonic elements of an auditory piece into a complete rendition, whether in music, film, or any other content of auditory nature. The finished piece, recorded or live, must achieve a good balance of properties, such as volume, pan positioning, and other effects, while resolving any arising frequency conflicts from various sound sources. These sound sources can comprise the different musical instruments or vocals in a band or orchestra, dialogue or Foley in a film, and more.

References

  1. ↑ "What's actually going on when people talk about digital vs. analogue masters". 18 October 2017.
  2. 1 2 Blair Jackson (May 1, 2006). "Issues in Modern Mastering". Mix Magazine. Archived from the original on May 24, 2007.
  3. 1 2 3 4 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. 1 2 3 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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