If the recordings are from one artist, then generally the tracks were not originally intended for release together as a single work,[1] but may be collected together as a greatest hits album or box set.
[2] If the recordings are from several artists, there may be a theme, topic, time period, or genre which links the tracks,[3][4] or they may have been intended for release as a single work—such as a tribute album.
[6] Songs included on a compilation album may be previously released or unreleased, usually from several separate recordings by either one or several performers.
[citation needed] According to sound technician Richard King, classical music compilations "may require more processing to match tracks coming from various sources and recording venues, as well as the different sizes of ensembles.
"[7] In Christgau's Record Guide: Rock Albums of the Seventies (1981), Robert Christgau said, "While compilation albums by album artists (as opposed to stylistically unified singles specialists) are often useless, sometimes they present themselves as events", citing as examples the 1971 Ray Charles LP A 25th Anniversary in Show Business Salute to Ray Charles, The Kink Kronikles (1972), and Changesonebowie (1976).