Sound recording
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Sound recording is the electrical or mechanical inscription and re-creation of sound waves, usually used for the voice or for music.
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.
The two main classes of sound recording technology are analog recording and digital recording.
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[change] Technology
[change] Analog cylinder
The first devices for recording sound were mechanical in nature. Invented by Thomas Alva Edison in 1877, the phonograph was a device with a cylinder on which a stylus drew grooves. The vertical vibrations of the needle corresponded to air pressure vibrations. The cylinder was covered with a soft material such as tinfoil, lead, wax or amberol. The recording could be played back by tracing a needle through the groove and amplifying the resulting vibrations. A disadvantage of the phonograph was the difficulty of reproducing the cylinders in mass production.
[change] Analog disk
This changed with the advent of the gramophone (what is known as the phonograph in American English), circa 1888. The gramophone works in much the same way as the phonograph, but instead of a cylinder record, the grooves are imprinted on a disk record. Reproduction of these disks was relatively simple by pressing a master image on a plate of shellac. The speed at with the disks were spun around were 78 rotations per minute (rpm). Later innovations allowed lower rotations: 45 and 33 rpm, and the material was changed to vinyl.
[change] Tape
In the late 1930's the tape recorder followed as the next step in the evolution of sound recording. This type of recording device uses a magnetic tape as recording medium. The tape is magnetized as it moves with a constant speed past a recording head. A tape allows multiple tracks in parallel to each other. This allowed for stereo sound (2 tracks), and quadrophonic sound (4 tracks). 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.
The evolution of the tape recording systems shows the evolution from analog to digital audio technology. The compact cassette contains 2 analog tracks per side. To improve the sound quality of the recording, tape recorders could use Dolby technology to boost the resolution of bass signals. Digital tape recorders were also available: Digital Audio Tape (DAT) recorded the raw audio sampled at 48 kHz with a resolution of 16 bits. DAT is still used in studios. A failed digital tape recording system is the Digital Compact Cassette (DCC).
[change] Compact Disc
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.
[change] Techniques
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 connect to it. The needle made the grooves in the recording medium.
To make this process as efficient as possible the diaphragm was located at the apex of a cone and the performer(s) 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. As a result of this, in 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 once the performance was still cut to to the recording medium, so if a mistake was made the recording was useless.
Electrical recording made it possible 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. In this way performances could be built up over time.
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 Audio editing
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 affects and the rearranging of parts of the recording.
