Compact audio cassetteFor the meaning of cassette in genetics, see cassette (genetics).
The compact audio cassette sound recording medium, sometimes known as the musicassette, was introduced by Philips in 1963. It consists of a length of magnetic recording tape inside a protective plastic shell. 4 tracks are available on the tape, giving 2 stereo tracks - one for playing with the cassette inserted with its 'A' side up, and the other with the 'B' side up, thus mimicking gramophone records.
On the grounds of convenience, this was a massive step forward from reel-to-reel recording, though the limitations of the cassette's size and speed compared poorly in quality. Unlike the open reel format, the two stereo tracks lie adjacent to each other rather than a 1/3 and 2/4 arrangement. The tape is 3.175 mm wide (an eighth of an inch) and moves at 47.625 mm/s (1 7/8 inch).
Tape length was usually measured in minutes total playing time, and the most popular varieties were C60 (30 minutes per side), C90, and C120 (usually thinner tape, more likely to be destroyed in use). Some vendors were more generous than others, providing 132 m or 135 m rather than 129 m for a C90 cassette.
Originally intended for use only in dictation machines it quickly became a medium for distributing pre-recorded music with an option for home recording use. Most cassettes were sold blank and used for recording the owner's records (to protect from wear or to make compilations), their friends' records, or music from the radio. This practice was sometimes condemned by the music industry with such slogans as "home taping is killing music". However, many opined that the medium was ideal for spreading new music and quite likely increased sales, and strongly defended at least their right to copy their own records onto tape. Cassettes were also a boon to people wishing to make 'bootlegs' for sale - unauthorised concert recordings.
Cassettes were also used for reputable purposes including journalism, field history, meeting transcripts and so on. Many home computers of the 1980s used cassettes as an inexpensive alternative to floppy disks as a storage medium for programs and data.
The original magnetic material was based on ferrite (Fe2O3), but then chromium dioxide (CrO2) and more exotic materials were used in order to improve sound quality to try to match those of vinyl records. These had different bias requirements, requiring more complicated equipment. Also used were a variety of noise reduction schemes, of which Dolby was the most pervasive. By the late 1980s, sound fidelity on equipment by manufacturers such as Nakamichi and Tandberg far surpassed the levels expected of the medium by early detractors.
Technical development of this medium effectively ceased when digital recordable media such as DAT and MiniDisc were introduced. Since the rise of cheap CD-R discs, the phenomenon of "home taping" effectively switched to compact disc.