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 term "classic rock" has retroactively been applied to these
artists and their music, to the point that some now consider "classic
rock" to be a musical genre unto itself.