The LP (Long Play) record is an audio format for phonograph records, introduced by Columbia Records in 1948 and still in use today.
LP records are made of vinyl (either virgin or recycled) and together with a playing speed of 33⅓ rpm and the use of microgrooves, allow for a playing time of around 45 minutes. Previously, 78 rpm records had a playing time of just around 3-4 minutes per side, so an ‘album’ of records was sold as a set, and this name continued to describe a collection of songs on a single disc.
Each side of an LP contains a single continuous groove, with an average length of 460 m.
LP records are generally 12 inches in diameter, but 10 inch LPs have also been produced at different times. The amount of vinyl in an LP is generally 130 g, but some records were produced with less (sometimes as little as 90 g). Modern high-fidelity LPs tend to use more, such as 180 g. Generally LPs are pressed on black vinyl, but coloured vinyl and picture discs (with a card sandwiched between two clear sides of vinyl) have been produced, as have shaped vinyl and even neon vinyl.
By as early as 1952, LPs represented 16.7% of unit sales, rising to 24.4% in 1958 (by then, most of the remainder was 45 rpm singles, 78 rpm only representing 2.1%).
Stereo sound was introduced in 1958, and quadraphonic records were sold in the 1970s for a time.
The LP had no serious competitors for long-playing recordings until the 1970s when the Compact Cassette improved in quality, and then in the 1980s with the introduction of the Compact Disc. LPs ceased to be a mainstream format in the early 1990s, but continue to be produced in small but increasing numbers.