Album oriented rock

Album-oriented rock (abbreviated AOR) is an American FM radio format focusing on album tracks by rock artists. AOR evolved from progressive rock radio in the mid-1970s, using research and formal programming to create an album rock format with greater commercial appeal.

The roots of the album-oriented rock radio format began with programming concepts rooted in 1960s idealism. The freeform and progressive formats developed the repertoire and set the tone that would dominate AOR playlists for much of its heyday.

In July 1964, the U.S. Federal Communications Commission (FCC) adopted a non-duplication rule prohibiting FM radio stations from merely running a simulcast of the programming from their AM counterparts. Owners of AM/FM affiliate stations fought these new regulations vigorously, delaying enactment of the new rules until January 1, 1967. When finally enacted, station owners were pressed to come up with alternative programming options.

The freeform format in commercial radio was born out of the desire to program the FM airwaves inexpensively. Programmers like Tom Donahue at KMPX in San Francisco developed stations where DJs had freedom to play long sets of music, often covering a variety of genres. Songs were not limited to hits or singles; indeed the DJs often played obscure or longer tracks by newer or more adventurous artists than heard on Top 40 stations of the day. This reflected the growth of albums as opposed to singles as rock's main artistic vehicle for expression in the 1960s and 1970s.

...
Wikipedia