The recording of sound is accomplished by representing, in some form susceptible of reproduction, the minute rapid fluctuations in air pressure that constitute sound. The first step was taken in 1857 by a Frenchman, Léon Scott, who found a means of representing soundwaves on a surface; but it was Thomas Edison, in 1877, who first made a recording (of ‘Mary had a little lamb’) that could be replayed, on his ‘phonograph’, essentially a grooved cylinder covered with tinfoil and rotated by a crank, connected by a sharp metal point to a speaking tube so that the point indented the foil in response to the vibrations. Its course could later be retraced by the metal point in order that they be reproduced. Flat discs were launched by Emil Berliner in 1896; this had the advantage of readier manufacture in quantity by production from a ‘master’ and ousted the cylinder by the 1920s. Recordings were acoustical (i.e. mechanical) in basis until the mid-1920s, when electrical recording was developed. A wider range of frequencies and dynamics could be impressed on the record, using electrical cutter heads. Discs were made of shellac, normally black; the standard 12-inch (30 cm) disc normally took 4 to 4½ minutes of music on each side, the ten-inch (25 cm) 3 to 31/3; most record companies adopted a standard speed of 78 rpm. The information cut on to each disc was in lateral rather than the original ‘hill-and-dale’ form, so that the needle followed a horizontal pattern rather than riding vertically.
In the late 1940s, the brittle, easily scratched and noisy shellac disc was replaced by softer, more flexible vinylite, capable of much finer grooves. These, revolving at 331/3-rpm (45 rpm for the small 7-inch, 18 cm, ‘single’ generally used for popular music or short pieces), could take up to 20 or 25 minutes of music per 12-inch side (more recently, well over 30 minutes without loss of quality). Stereophonic records were introduced in 1957, involving the engraving on the disc of two sets of information in different planes and transmitting them to two distinct amplifying and reproduction systems; this gives an effect of spatial reproduction instead of compressing the original sound into a single source. A four-channel (‘quadraphonic’) system was also evolved but proved not to be susceptible of commercial development. The rise of the LP (long-playing) record was much assisted by the development of magnetic tape for recording, which meant that, with careful editing, long stretches of music could be assembled from several ‘takes’ to produce ‘perfect’ performances. In 1979 this sytem was further improved by the application of digital (instead of the existing analogue) systems to recording and editing; its basis is the use of computerized systems for the instant storage of the wave-form and its reconversion into sound. Digital systems were applied to the playback process when, in 1983, the CD (compact disc) was made available: here a metal disc, 4. 7 inches in diameter, and capable of storing more than an hour's music, is inscribed with a microscopic pattern of dots in spiral form, in a binary code, which is read by a laser beam of infra-red light that converts the musical information into sound. This not only permits much longer stretches of music to be heard at a single, continuous sitting (well over an hour), but also allows the listener to select any track or movement instantaneously and provides a much clearer and more faithful sound reproduction with no accompanying noise.
