Sound recording

From Academic Kids

Methods and media for sound recording are varied and have undergone significant changes between the first time sound was actually recorded for later playback until now.

Bennett (1980, p.114) describes the development of recording consciousness, the consequence of "a society which is literally wired for sound" in which, according to Middleton (1990, p.88) "this consciousness defines the social reality of popular music." "Acoustic instruments and unamplified, 'pure'-tone singing can now not be heard except as contrasts to more recent kinds of sounds, just as live perfromances are inevitably 'checked' against memories of recordings," and "live performances have to try to approximate the sounds which inhabit this consciousness."



Mechanical Recording

The first devices for recording sound were mechanical in nature.

In 1796 a Swiss watchmaker named Antoine Favre described his idea for what we now call the cylinder musical box. This can be considered an early method of recording a melody, although it does not record an arbitrary sound and does not record automatically. "Playback" however is automatic.

The Player piano was a device that could playback a piano performance which had earlier been mechanically recorded onto a piano roll.

The first recording of sound waves

Leon Scott invented the 'phonoautograph', the first device to record arbitrary sound in 1857. It used a membrane (which vibrated in response to sound) attched to a pen, which traced a line roughly corresponding to the sound wave form on to a moving roll of paper. Although able to record sound, the phonoautograph was unable to play back the recording; it was of little use other than as a laboratory curiosity. (In one laboratory experiment, a phonoautograph recording was photoengraved onto a metal plate, creating a groove, which was then played back).

The Phonograph and the Gramophone

The phonograph built expanding on the principles of the phonoautograph. Invented by Thomas Edison in 1877, the phonograph was a device with a cylinder covered with a soft material such as tin foil, lead, or wax on which a stylus drew grooves. The depth of the grooves made by the stylus corresponded to change in air pressure created by the original sound. The recording could be played back by tracing a needle through the groove and amplifying, through mechanical means, the resulting vibrations. A disadvantage of the early phonographs was the difficulty of reproducing the phonograph cylinders in mass production.

This changed with the advent of the gramophone (phonograph in American English), which was patented by Emile Berliner in 1887. The gramophone imprinted grooves on the flat side of a disc rather than the outside of a cylinder. Instead of recording the varying the depth of the groove (vertically), as with the phonograph, the vibration of the recording stylus was across the width of the track ( horizontally). The depth of the groove remained constant. Berliner called this audio disc a "gramophone record", although it was often called a "phonograph record" in U.S. English.

Early disc recordings and phonograph cylinders had about the same audio fidelity (despite the cylinder's theoretical advantages of constant linear groove speed and greater dynamic range of the hill-and-dale groove geometry). However, disc records were easier and cheaper to mass produce. From the beginning, the flat disks were easily mass-produced by a molding process, pressing a master image on a plate of shellac.

Originally, cylinders could only be copied by means of a pantograph mechanism, which was limited to making about twenty-five copies—all of significantly lower quality than the original—while simultaneously destroying the original. During a recording session, ten or more machines could be ranged around the talent to record multiple originals. Still, a single performance could produce only a few hundred salable copies, so performers were booked for marathon sessions in which they had to repeat their performances over and over again. By the mid-1900s, successful molding processes for cylinder recordings were developed, but by then disks had gained the ascendancy.

The speed at with the disks were rotated was eventually standardized at 78 rpm. Later innovations allowed lower rotations: 45 and 33⅓ rpm, and the material was changed to vinyl.

Both phonograph cylinders and gramophone discs were played on mechanical devices most commonly hand wound with a clockwork motor. The sound was amplified by a cone that was attached to the diaphragm. The disc record largely supplanted the competing cylinder record by the late 1910s.

The advent of electrical recording in 1924 drastically improved the quality of the recording process of disc records. Oddly, there was a period of nearly five years, from 1925 to 1930, when the premiere technology for home sound reproduction consisted of a combination of electrically recorded records with the specially-developed Victor Orthophonic phonograph, a spring-wound acoustic phonograph which used waveguide engineering and a folded horn to provide a reasonably flat frequency response. Electrically-powered phonographs were introduced c. 1930, but crystal pickups and electronic reproduction did not become common until the late 1930s.

Magnetic Recording

Magnetic recording was demonstrated in principle as early as 1898 by Valdemar Poulsen in his telegraphone. Magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves with a constant speed past a recording head. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal. A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal.

With the addition of electronic amplification developed by Curt Stille in the 1920s, the telegraphone evolved into wire recorders which were popular for voice recording and dictation during the 1940s and into the 1950s. The reproduction quality of wire recorders was low, however — significantly lower than that achievable with phonograph disk recording technology. Wire recorders could not prevent the wire from undergoing axial twisting, and hence could not ensure that the wire was oriented the same way during recording and playback. When oriented the wrong way, high frequencies were reduced and the sound was muffled. The hysteresis of the steel material resulted in nonlinear transfer characteristics, manifesting as distortion. There were other practical difficulties, such as the tendency of the wire to become tangled or snarled. Splicing could be performed by knotting together the cut wire ends, but the results were not very satisfactory.

Early tape recorders were first developed in Germany. On Christmas day 1932 the British Broadcasting Corporation first used a tape recorder for their broadcasts. The device used was a Marconi-Stille recorder, a huge tape machine which used steel razor tape 3mm wide and 0.08mm thick. In order to reproduce the higher audio frequencies it was necessary to run the tape at a 90 metres per minute past the recording and reproducing heads. This meant that the length of tape required for a half-hour programme was nearly 3 kilometres and a full reel weighed 25kg!

open reel magnetic tape
open reel magnetic tape

Magnetic tape recording as we know it today was developed in Germany during the late 1930s by the C. Lorenz company and by AEG . In 1938, S. J. Begun left Germany and joined Brush Development Company in the United States, where work continued but attracted little attention.

Engineers at AEG, working with the chemical giant I.G. Farben, created the world's first practical magnetic tape recorder, the 'K1', which was first demonstrated in 1935. During World War II AEG engineers discovered the AC biasing technique. A high-frequency signal, typically in the range of 50 to 150 kHz, is added to the audio signal before being applied to the recording head. This means that the magnetization is performed at levels in the most linear portion of the medium's transfer function. Biasing radically improved sound quality and enabled them to develop their recorders to new heights of technical excellence; by 1943 they had developed stereo tape recorders.

During the war, the Allies became aware of radio broadcasts that seemed to be transcriptions (much of this due to the work of Richard_H._Ranger), but their audio quality was indistinguishable from that of a live broadcast and their duration was far longer than was possible with 78rpm discs. At the end of the war, the Allied capture of a number of German Magnetophon recorders from Radio Luxembourg aroused great interest. These recorders incorporated all of the key technological features of analog magnetic recording, particular the use of high-frequency "bias."

Development of magnetic tape recorders in the late 1940s and early 1950s is associated with the Brush Development Corporation and its licensee, Ampex; the equally important development of magnetic tape media itself was led by Minnesota Mining and Manufacturing corporation (now known as 3M).

American audio engineer John T. Mullin and entertainer Bing Crosby were key players in the commercial development of magnetic tape. Mullin served in the U.S. Army Signal Corps and was posted to Paris in the final months of WWII; his unit was assigned to find out everything they could about German radio and electronics, including the investigation of claims that the Germans had been experimenting with high-energy directed radio beams as a means of disabling the electrical systems of aircraft. Mullin's unit soon amassed a collection of hundreds of low-quality magnetic dictating machines, but it was a chance visit to a studio at Bad Neuheim near Frankfurt while investigating radio beam rumours, that yielded the real prize.

Mullin was given two suitcase-sized AEG 'Magnetophon' high-fidelity recorders and fifty reels of recording tape. He had them shipped home and over the next two years he worked on the machines constantly, modifying them and improving their performance. His major aim was to interest Hollywood studios in using magnetic tape for movie sound recording.

Mullin gave two public demonstrations of his machines, and they caused a sensation among American audio professionals -- many listeners literally could not believe that what they were hearing was not a live performance. By luck, Mullin's second demonstration was held at MGM studios in Hollywood and in the audience that day was Bing Crosby's technical director, Murdo Mackenzie. He arranged for Mullin to meet Crosby and in June 1947 he gave Crosby a private demonstration of his magnetic tape recorders.

Crosby was stunned by the amazing sound quality and instantly saw the huge commercial potential of the new machines. Live music was the standard for American radio at the time and the major radio networks didn't permit the use of disc recording in many programs because of their comparatively poor sound quality. But Crosby disliked the regimentation of live broadcasts, preferring the relaxed atmosphere of the recording studio. He had asked NBC to let him pre-record his 1944-45 series on transcription discs, but the network refused, so Crosby had withdrawn from live radio for a year, returning for the 1946-47 season only reluctantly.

Mullin's tape recorder came along at precisely the right moment. Crosby realised that the new technology would enable him to pre-record his radio show with a sound quality that equalled live broadcasts, and that these tapes could be replayed many times with no appreciable loss of quality. Mullin was asked to tape one show as a test and was immediately hired as Crosby's chief engineer to pre-record the rest of the series.

Crosby became the first major American music star to use tape to pre-record radio broadcasts, and the first to master commercial recordings on tape. The taped Crosby radio shows were painstakingly edited (by hand) to give them a pace and flow that was wholly unprecedented in radio. Mullin even claims to have been the first to use "canned laughter"; at the insistence of Crosby's head writer, Bill Morrow, he inserted a segment of raucous laughter from an earlier show into a joke in a later show that hadn't worked well.

Keen to make use of the new recorders as soon as possible, Crosby invested $50,000 of his own money into Ampex, and the tiny six-man concern soon became the world leader in the development of tape recording, revolutionising radio and recording with its famous Model 200 tape deck, issued in 1948 and developed directly from Mullin's modified Magnetophones.

Working with the brilliant Mullin, Ampex rapidly developed two-track stereo and then three-track recorders. Spurred on by Crosby's move into television in the early 1950s, Mullin and Ampex had developed a working monochrome videotape recorder by 1950 and a colour recorder by 1954, both created to tape Crosby's TV shows.


7½" reel of ¼" recording tape
Typical of audiophile/consumer/educational use 1950s-60s

The typical professional tape recorder of the early 1950s used ¼" wide tape on 10½" reels, with a capacity of 2400 feet (731.5 metres). Typical speeds were initially 15 in/s (38.1 cm/s) yielding 30 minutes' recording time on a 2400 ft (730 m) reel. 30 in/s (76.2 cm/s) was used for the highest quality work.

Standard tape speeds varied by factors of two. 15 and 30 in/s were used for professional audio recording; 7½ in/s (19 cm/s) for home audiophile prerecorded tapes; 7½ and 3¾ in/s (19 and 9.5 cm/s) for audiophile and consumer recordings (typically on 7 in or 18 cm reels). 17/8; in/s (4.76 cm/s) and occasionally even 15/16 in/s (2.38 cm/s) were used for voice, dictation, and applications where very long recording times were needed, such as logging police and fire department calls.

Multitrack recording

The next major development in magnetic tape was multitrack recording, in which the tape is divided into multiple tracks parallel with each other. Because they are carried on the same medium, the tracks stay in perfect synchronization. The first development in multitracking was stereo sound, which divided the recording head into two tracks. First developed by German audio engineers ca. 1943, 2-track recording was rapidly adopted for classical music in the 1950s because it enabled signals from two or more separate microphones to be recorded simultaneously, enabling stereophonic recordings to be made and edited conveniently. (The first stereo recordings, on disks, had been made in the 1930s, but were never issued commercially.) Stereo (either true, two-microphone stereo or multimiked) quickly became the norm for commercial classical recordings and radio broadcasts, although many pop music and jazz recordings continued to be issued in monophonic sound until the mid-1960s.

Much of the credit for the development of multitrack recording goes to guitarist, composer and technician Les Paul, who also designed the famous electric guitar that bears his name. His experiments with tapes and recorders in the early 1950s led him to develop the first 3-track recorder, and his pioneering recordings with his then wife, singer Mary Ford, were the first to make use of the technique of multitracking to record separate elements of a musical piece asynchronously - that is, separate elements could be recorded at different times, and Paul's invention enabled him to listen to the tracks he had already taped and record new parts in time alongside them.

Paul's invention was immediately taken up by Ampex, who soon produced a commercial 3-track recorder. These proved extremely useful for popular music, since they enabled backing music to be recorded on two tracks (either to allow the overdubbing of separate parts, or to create a full stereo backing track) while the third track was reserved for the lead vocalist. Three-track recorders remained in widespread commercial use until the mid-1960s and many famous pop recordings -- including many of Phil Spector's "Wall of Sound" productions and early Motown hits -- were taped on Ampex 3-track recorders.

The next important development was 4-track recording. The advent of this improved system gave recording engineers and musicians vastly greater flexibility for recording and overdubbing, and 4-track was the studio standard for most of the later 1960s. Many of the most famous recordings by The Beatles and The Rolling Stones were recorded on 4-track, and the engineers at London's Abbey Road Studios became particularly adept at a technique called "bouncing down", in which multiple tracks were built up on one 4-track machine and then transferred (bounced down) to one track of a second 4-track machine. In this way, it was possible to record literally dozens of separate tracks and combine them into finished recordings of great complexity.

All of the Beatles classic mid-60s recordings, including the albums Revolver and Sgt Pepper's Lonely Hearts Club Band, were recorded in this way. There were limitations, however, because of the build-up of noise during the bouncing-down process, and the Abbey Road engineers are still justly famed for the ability to create dense multitrack recordings while keeping background noise to a minimum.

4-track tape also enabled the development of quadrophonic sound, in which each of the four tracks was used to simulate a complete 360-degree surround sound. A number of albums including Pink Floyd's Dark Side of the Moon and Mike Oldfield's Tubular Bells were released both in stereo and quadrophonic format in the 1970s, but 'quad' failed to gain wide commercial acceptance. Although it is now considered a gimmick, it was the direct precursor of the surround sound technology that has become standard in many modern home theatre systems.

In a professional setting today, such as a studio, audio engineers may use 24 tracks or more for their recordings, one (or more) tracks for every instrument played.

Magnetic audio tape can be easily and inaudibly spliced. The combination of the ability to edit via splicing, and the ability to record multiple tracks, revolutionized studio recording. It became common studio recording practice to record on multiple tracks, and mix down afterwards. The convenience of tape editing and multitrack recording led to the rapid adoption of magnetic tape as the primary technology for commercial musical recordings. Although 331/3; rpm and 45 rpm vinyl records were the dominant consumer format, recordings were customarily made first on tape, then transferred to disk, with Bing Crosby leading the way in the adoption of this method in the United States.

Analog magnetic tape recording introduces noise, usually called "hiss", caused by the finite size of the magnetic particles in the tape. There is a direct tradeoff between noise and economics. Signal-to-noise ratio is increased at higher speeds and with wider tracks, decreased at lower speeds and with narrower tracks.

By the late 1960s, disk reproducing equipment became so good that audiophiles soon became aware that some of the noise audible on recordings was not surface noise or deficiencies in their equipment, but reproduced tape hiss. A few companies starting making "direct to disk" specialty recordings, made by feeding microphone signals directly to a disk cutter (after amplification and mixing). These recordings never became popular, but they dramatically demonstrated the magnitude and importance of the tape hiss problem.

Missing image
audio cassette

Prior to 1963, when Philips introduced the Compact audio cassette, almost all tape recording had used the reel-to-reel (also called "open reel") format. Previous attempts package the tape in a convenient cassette that required no threading met with limited success; the most successful was 8-Track cartridge used primarily in automobiles for playback only. The Philips Compact audio cassette added much needed convenience to the tape recording format and quickly came to dominate the consumer market, although it was lower in quality than open reel formats.

In the 1970s, advances in solid-state electronics made the design and marketing of more sophisticated analog circuitry economically feasible. This led to a number of attempts to reduce tape hiss through the use of various forms of volume compression and expansion, the most notable and commercially successful being several systems developed by Dolby Laboratories. These systems divided the frequency spectrum into multiple bands and applied volume compression/expansion independently to each band. The Dolby systems were very successful at increasing the effective dynamic range and signal-to-noise ratio of analog audio recording; to all intents and purposes, audible tape hiss could be eliminated. The original Dolby A was only used in professional recording. Successors found use in both professional and consumer formats; Dolby B became almost universal for the compact cassette, both prerecorded and for home use.

In the 1980s, digital recording methods were introduced, and analog tape recording was gradually displaced. Digital audio tape never became important as a consumer recording medium partially because of legal complications arising from piracy fears on the part of the record companies. They had opposed magnetic tape recording when it first became available to consumers, but the technical difficulty of juggling recording levels, overload distortion, and residual tape hiss was sufficiently high that magnetic tape piracy never became an unsurmountable commercial problem. With digital methods, copies of recordings could be exact, and piracy might have become a serious commercial problem. The introduction of the audio CD occurred about the same time and the record companies heavily pushed this due to the fact it could not be home recorded. However cd recorders have since become available. Digital tape is still used in professional situations and the DAT variant has found a home in computer data backup applications.

Recording on Film

The first attempts to record sound to an optical medium occurred around 1900. In 1906 Lauste applied for a patent to record sound on film, but was ahead of his time. In 1923 de Forest applied for a patent to record to film. In 1927 the sound film The Jazz Singer was released; while not the first, it made a tremendous hit and made the public and the film industry realize that sound film was more than a mere novelty.

The Jazz Singer used a process called Vitaphone, a process that involved synchronizing the projected film to sound recorded on disk. It essentially amounted to playing a phonograph record, but one that was recorded with the best electronic technology of the time. Audiences used to acoustic phonographs and recordings would, in the theatre, have heard something resembling 1950s "high fidelity."

In the days of analog technology, however, no process involving a separate disk could hold synchronization precisely or reliably. Vitaphone was quickly supplanted by technologies which recorded a sound track optically directly onto the side of the strip of motion picture film. This was the dominant technology from the 1930s through the 1960s and is still in use as of 2004.

There are two primary methods for optical recording on film. Variable density recording uses changes in the darkness of the soundtrack side of the film to represent the soundwave. Variable width recording uses changes in the width of a dark strip to represent the soundwave.

In both cases light that is sent through the part of the film that corresponds to the soundtrack changes in intensity, proportional to the original sound, and that light is not projected on the screen but converted into an electrical signal by a light sensitive device.

In the late 1950s the cinema industry, desperate to provide a theatre experience that would be overwhelmingly superior to television, introduced wide-screen processes such as Cinerama, Todd-AO, and CinemaScope. These processes at the same time introduced technical improvements in sound, generally involving the use of multitrack magnetic sound, recorded on an oxide stripe laminated onto the film. In subsequent decades, a gradual evolution occurred with more and more theatres installing various forms of magnetic-sound equipment.

In the 1990s, digital systems were introduced and began to prevail. Ironically, in many of them the sound recording is, as in Vitaphone, again recorded on a separate disk; but now, digital processes can achieve reliable and perfect synchronization.

Digital Recording

The first digital audio recorders were reel-to-reel decks introduced by companies such as Denon (1972), Soundstream (1979) and Mitsubishi. They used a digital technology known as PCM recording. Within a few years, however, many studios were using devices that encoded the digital audio data into a standard video signal, which was then recorded on a U-matic or other videotape recorder, using the rotating-head technology that was standard for video. A similar technology was used for a consumer format, Digital Audio Tape (DAT) which used rotating heads on a narrow tape contained in a cassette. DAT records at sampling rates of 48kHz or 44.1kHz, the latter being the same rate used on compact discs. Bit depth is 16 bits, also the same as compact discs. DAT was a failure in the consumer-audio field (too expensive, too finicky, and crippled by anti-copying regulations), but it became popular in studios (particularly home studios) and radio stations. A failed digital tape recording system was the Digital Compact Cassette (DCC).

Within a few years after the introduction of digital recording, multitrack recorders (using stationary heads) were being produced for use in professional studios. In the early 1990s, relatively low-priced multitrack digital recorders were introduced for use in home studios; they returned to recording on videotape.

In the consumer market, tapes and gramophones were largely displaced by the compact disc (CD) and a lesser extent the minidisc. These recording media are fully digital and require complex electronics to play back.

Sound files can be stored on any computer storage medium. The development of the MP3 audio file format, and legal issues involved in copying such files, has driven most of the innovation in music distribution since their introduction in the late 1990s.

As hard disk capacities and computer CPU speeds increased at the end of the 1990s, hard disk recording became more popular. At this writing (early 2005) hard disk recording takes two forms. One is the use of standard desktop or laptop computers, with adapters for encoding audio into two or many tracks of digital audio. These adapters can either be in-the-box soundcards or external devices, either connecting to in-box interface cards or connecting to the computer via USB or Firewire cables. The other common form of hard disk recording uses a dedicated recorder which contains analog-to-digital and digital-to-analog converters as well as one or two removable hard drives for data storage. Such recorders, packing 24 tracks in a few units of rack space, are actually single-purpose computers, which can in turn be connected to standard computers for editing.


The earliest methods of recording sound involved the live recording of the performance directly to the recording medium. This was an entirely mechanical process, often called "Acoustical recording". The sound of the performers was captured by a diaphragm with the cutting needle connected to it. The needle made the groove in the recording medium.

To make this process as efficient as possible the diaphragm was located at the apex of a cone and the performers would crowd around the other end. If a performer was too loud then they would need to move back from the mouth of the cone to avoid drowning out the other performers. In some early Jazz recordings a block of wood was used in place of the bass drum.

The advent of electrical recording made it possible to use microphones to capture the sound of the performance. The leading record labels switched to the electric microphone process in 1925, and most other record companies followed their lead by the end of the decade. Electrical recording increased the flexibity and sound quality. However, the performance was still cut directly to the recording medium, so if a mistake was made the recording was useless.

Electrical recording made it more feasible to record one part to disc and then play that back while playing another part, recording both parts to a second disc. This is called over-dubbing. The first commercially issued records using over-dubbing were released by the Victor Talking Machine Company in the late 1920s. However overdubbing was of limited use until the advent of analogue audio tape. Use of tape overdubbing was pioneered by Les Paul and is called 'sound on sound' recording. Studios thus could create recorded "performances" that could not be duplicated by the same artists performing live.

The analogue tape recorder made it possible to erase or record over a previous recording so that mistakes could be fixed. Another advantage of recording on tape is the ability to cut the tape and join it back together. This allows the recording to be edited. Pieces of the recording can be removed, or rearranged. See also audio editing, audio mixing, multitrack recording.

The advent of electronic instruments (especially keyboards and synthesisers), effects and other instruments has led to the importance of MIDI in recording. For example, using MIDI timecode, it is possible to have different equipment 'trigger' without direct human intervention at the time of recording.

In more recent times, computers (digital audio workstation) have found an increasing role in the recording studio, as their use eases the tasks of cutting and looping, as well as allowing for instantaneous changes, such as duplication of parts, the addition of effects and the rearranging of parts of the recording.

See also



  • Middleton, Richard (1990/2002). Studying Popular Music. Philadelphia: Open University Press. ISBN 0335152759.



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