Classic rock was originally conceived as a radio station programming format which evolved from the album oriented rock (AOR) format in the mid-1980s. In the United States, this rock music format now features a limited playlist of songs ranging from late 1960s through today with more emphasis on the earlier hits by artists associated with the loosely-defined "classic rock era".
The origins of the classic rock radio format can be traced back to The Beatles' groundbreaking album Sgt. Pepper's Lonely Hearts Club Band, which would forever change several courses of the rock and roll format, especially with the slow rise of FM broadcasting, even though a majority of people were still listening to AM radio. Since Sgt. Pepper did not spawn any singles, both AM and FM stations began to play select tracks from the album in an attempt to retain listeners. Soon both stations and artists realized that album cuts rather than Top 40-oriented singles could be a major source of radio airplay and artist visibility.
Taken to the furthest level, this created what would be called progressive rock radio in the late 1960s and 1970s. This format was associated with elements of freeform radio, where disc jockeys controlled what was played. Soon a more commercially-oriented variant called Album Oriented Rock (AOR), or "album rock", emerged in the mid- and late 1970s. This format concentrated on album cuts as well, but on a more structured, playlist-oriented basis.
AOR would continue to be popular in the 1970s and early 1980s, but by the end of the 1980s, as "albums" had been supplanted by compact discs and as station playlists largely stopped keeping up with developing musical trends (including new wave music), "album rock" evolved into "classic rock" on many of these FM radio stations.
The first station to switch to an all-old rock format and call itself "classic rock" on the air was WYSP-FM in Philadelphia in January 1981. Program director/WYSP midday personality Dick Hungate met with station consultant Lee Abrams and together they decided to counter then-dominant (and traditionally-programmed) Philly album rockers WMMR and WIOQ with a songlist of 100% already-established and popular hits and older album tracks. After first considering the on-air describers "vintage" and "timeless", Hungate and Abrams settled on the word "classic". Hungate had to come up with the on-air presentation, or "format" in which songs were picked and then divided up according to age or perceived appeal/strength. His work at WMMR as midday man and music director two years earlier (under PD Jeff Pollack, who would go on to become an influential rock radio consultant with Pollack Media Group) helped Hungate by gut feel create the universe of appropriate classic tracks. From there, the format spread to KQRS-FM in Minneapolis and later to the rest of the country.
Classic rock is similar to oldies radio in that the format is based upon music of the past, hence the playlist and artists featured are relatively stable in comparison to Top 40 or other contemporary formats which are based primarily on current releases. However, various bands and songs will come in and out of style on classic rock radio, and regional favorites may be featured in a particular market. Additionally, in the process of jockeying for position and listener share in competetive markets, stations will often add songs and artists only marginally associated with the classic rock era, and some stations combine the classic rock format with other formats, including modern rock in an attempt to increase popularity. The hybrid of classic rock and modern rock is also referred to as active rock.