Pop Organ Varieties / Reader's Digest 4x Discs / RDA 46-A​

The LP (from "long playing" or "long play") is an analog sound storage medium, 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 vinyl composition disk. Introduced by Columbia in 1948, it was soon adopted as a new standard by the entire record industry.