LP record
The LP (from long playing or long play) is an analog sound storage medium, specifically a phonograph record format characterized by a speed of 33+1⁄3 rpm, a 12- or 10-inch (30- or 25-cm) diameter, use of the "microgroove" groove specification, and a black vinyl (a copolymer of vinyl chloride acetate) composition disk. Introduced by Columbia Records in 1948, it was soon adopted as a new standard by the entire US record industry and, apart from a few relatively minor refinements and the important later addition of stereophonic sound in 1957, it remained the standard format for record albums during a period in popular music known as the "album era".