MUSIC & TECHNOLOGY: RECORDED SOUND

INTRODUCTION

Mankind has always been fascinated by the idea of capturing sound. Early attempts included mechanical music performed by self-playing instruments, determined by a program in the form of a pinned cylinder or a punched disc or strip. E.g. music box, barrel organ, pianola, orchestrion.

ANALOG SOUND

Acoustical or mechanical era

Sound recording and reproduction was made by mechanical means without using electricity or magnetism.

1. Édouard-Léon Scott invented the phonautograph in 1857, that didn't record sound but a graphical image of it called phonautogram. Scott made the oldest known intelligible recordings of the human voice.

2. Thomas Alva Edison invented the phonograph in 1877, which used a tinfoil cylinder to record sound and play it back. It was not intended for recording music but for dictation.

Recording: A horn captures the sound and transmits it into a diaphragm attached to a recording needle that cuts vertical grooves of varying depth into a rotating tinfoil cylinder.
The recording is called phonogram. Musicians perform crowded together into a large horn. Adjustments to the sound were made by altering the performer's position relative to the horn or by trying horns of differing sizes or diaphragms of varied thickness.

Reproduction: The reading needle picks up vibrations as it moves through the grooves of the cylinder, which are transformed by the diaphragm into sound waves and transmitted to the air through the horn.
These recordings reproduced the sound with a very limited frequency range and very distorted.

3. Alexander Graham Bell created the graphophone in 1886, which used a wax cylinder. These recordings could not be duplicated but they allowed better sound quality and were longer.

4. Emile Berliner invented the gramophone in 1887, which used a flat disc recorded on one side cutting lateral grooves, from side-to-side instead of up-and-down. He was the first to mass-produce copies from a zinc master disc by stamping them out into hard rubber originally and shellac later. He began to sell a playback-only device for consumers and the sale of recorded music developed into a business.

Common audio formats:

Tinfoil cylinder: format of phonograph recordings with a 2 or 3 minute capacity.
Wax cylinder: format of graphophone recordings with a 4 minute capacity.
78 rpm disc: format of gramophone recordings with a 6 minute capacity, 25 cm diameter and 78 revolutions-per-minute speed. It required less storage space and it was used until 1960.

Electrical era

Western Electric engineers created a technology based in several radio-related developments in the 1920s.

Recording: A microphone converts sound into an electrical signal which is amplified activating the recording needle that cuts grooves into a record.
Musicians recorded in the same seating arrangement for live concerts. Sound quality was improved with a wider frequency and dynamic range. Alan Blumlein created the stereophonic recording in 1931 with two microphones and two needles cutting two tracks on the same disc. But it was not popular until the 1960s.

Reproduction: The reading needle on a record picks up vibrations, which are turned into an electrical signal by a cartridge and amplified by a loudspeaker.
During the 1930s the electric record player or turntable entered the home.

Common audio formats:

LP or 33 1⁄3 rpm Long Play record: format with a 30 cm diameter and 25 minutes per side introduced by Columbia in 1948, that became the standard for vinyl albums and it's still in use today.
Single or 45 rpm record: format with a 18 cm diameter and 5 minutes per side which contains one song on the A-side and another song on the B-side. It became popular in jukeboxes.
EP or Extended Play record: format with a 18 cm diameter which contains more songs than a single but not as many as the LP.

Magnetic era

Valdemar Poulsen created the telegraphone in 1898, which magnetically recorded sound on a metal wire.
Fritz Pfleumer invented the magnetic tape in 1928 and AEG developed the magnetophon in 1935, a reel-to-reel tape recorder. This technology remained restricted to Germany until the end of World War II.

Recording: A microphone converts sound into an electrical signal which is amplified. The recording head turns this signal into variations of the magnetic field and impresses them on the moving tape so the grains of iron oxide form a pattern.
The magnetic tape is a plastic strip coated with grains of iron oxide which are arranged irregularly on a blank tape and they form a pattern on a recorded tape. These recordings allowed tape editing, multi-tracking, longer recordings and more sound quality that is better preserved when duplicated. A professional tape recorder has 3 heads: eraser-recorder-player, although the same head can be used for recording and playback.

Reproduction: The playback head turns a changing magnetic field on the tape into an electrical signal, then amplified by the loudspeaker.

Common audio formats: 4-track cartridge, 8-track cartridge.

Reel-to-reel tape: format with magnetic tape on open reels, that was expensive and difficult to use, so it was used by professionals in radio and recording studios.
Compact cassette: format with magnetic tape on two reels protected by a plastic shell and 30 minutes per side. It was introduced by Philips in 1963 and became popular until the 1990s being replaced by CD. Famous players include boombox and walkman, which are portable and enabled users to take their music anywhere.

DIGITAL SOUND

Digital era

Recording: A microphone converts sound into an electrical signal and an analog-to-digital converter (ADC) transforms it into a signal that samples the sound wave and expresses it as binary numbers (1 or 0). A high-quality recording requires a sampling rate of at least 40,000 Hz (samples per second). The digital signal can be recorded, edited and stored onto a CD, hard drive or streamed online.
These recordings became the new standard at every level, professional and domestic.

Reproduction: A DAC (digital-to-analog converter) turns the digital signal back into an analog signal, then amplified by the loudspeaker.

Common audio formats: laserdisc, minidisc, digital audio tape (DAT), digital compact cassette (DCC), etc.

Compact disc (CD): digital audio format with 80 minute capacity and a sampling rate of 44.100 Hz, which is encoded and read optically using a laser beam. It was introduced by Philips and Sony in 1982 and it became popular in the 1990s.

Digital audio file: format that eliminated the need of a physical medium and facilitated the illegal sharing of copyrighted media by file sharing technologies such as Napster and BitTorrent.
- WAV: uncompressed digital audio format introduced by Microsoft and IBM in 1991, with the same quality as an audio CD. These files are very large (1 minute = 10 MB).
- MP3: compressed digital audio format introduced by Fraunhofer IIS in 1993, which discards some of the information undetectable to the human ear. The size of these files was reduced (1 minute = 1 MB) using lossy compression. Famous playback devices include MP3 players and iPod. It became the most popular format.
- OGG: free container format in which the contained audio can be compressed using lossy codecs (Vorbis) or lossless codecs (Flac). Lossless compression doesn't discard information so the encoded audio is identical to the original. Ogg Vorbis is used by streaming services such as Spotify.