The album era was a period in popular music, usually defined as the mid-1960s through the mid-2000s, in which the album—a collection of songs issued on physical media—was the dominant form of recorded music expression and consumption. It was driven primarily by three storage formats: the 33⅓ rpm long-playing record (LP), the cassette tape, and the compact disc (CD). Rock musicians from the US and UK were often at the forefront of the era. The term "album era" is also used to refer to the marketing and aesthetic period surrounding a recording artist's release of an album.