Album-oriented rock (abbreviated AOR) is an American FM radio format focusing on album tracks by rock artists. AOR evolved from progressive radio in the mid-1970s, using research and formal programming to create an album rock format with greater commercial appeal.
Freeform and progressive 
The roots of the album-oriented rock radio format began with programming concepts rooted in 1960s idealism. The freeform or 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 this desperate need to program the FM airwaves inexpensively. Programmers like Tom Donahue at KMPX and Ron Elz at KSHE in St. Louis 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.
With a few exceptions, commercial freeform had a relatively brief life. With more and more listeners acquiring FM radios, the stakes became higher for stations to attract market share so that they could sell more advertising at a higher rate.
By 1970 many of the stations were moving to institute programming rules with a "clock" and system of "rotation". With this shift, stations' formats in the early 1970s were now billed as progressive. DJs still had much input over the music they played, and the selection was deep and eclectic, ranging from folk to hard rock with other styles such as jazz fusion occasionally thrown in.
Album-oriented rock 
In the mid-1970s, as program directors began to put more controls over what songs were played on air, progressive stations evolved into the album-oriented rock format. Stations still played longer songs and deep album tracks (rather than just singles), but program directors and consultants took on a greater role in song selection, generally limiting airplay to just a few “focus tracks” from a particular album and concentrating on artists with a more slickly produced "commercial" sound than what had been featured a few years earlier. Noted DJ "Kid Leo" Travagliante of influential station WMMS in Cleveland observed the changes in a 1975 interview: "I think the '60s are ending about now. Now we are really starting the '70s. The emphasis is shifting back to entertainment instead of being 'relevant'...In fact, I wouldn't call our station progressive radio. That's outdated. I call it radio. But I heard a good word in the trades, AOR. That's Album-Oriented Rock. That's a name for the '70s." The term "album-oriented rock" was coined by Radio & Records editor Mike Harrison, who developed the format while program director at KPRI in San Diego from 1973 to 1975.
By the late 1970s, AOR radio discarded the wide range of genres embraced earlier on to focus on a more narrowly defined rock sound. The occasional folk, jazz, and blues selections became rarer and most black artists were effectively eliminated from airplay. Where earlier soul and R&B artists like Stevie Wonder, War, Sly Stone and others had been championed by the format, AOR was no longer representing these styles, and took a stance against disco. In 1979, Steve Dahl of WLUP in Chicago destroyed disco records on his radio show, culminating in the notorious Disco Demolition Night at Comiskey Park.
What links the freeform, progressive, AOR and ultimately the classic rock formats are the continuity of rock artists and songs carried through each phase. Programmers and DJs of the freeform and progressive phases continued to cultivate a repertoire of rock music and style of delivery that were foundations of AOR and now classic rock. Those AOR stations, which decided to stay "demographically-rooted", became classic rock stations by eschewing newer bands which their older listeners might tune out. Those that did not fully evolve into classic rock generally attempt to hold onto their older listeners through careful dayparting—playing large amounts of classic rock during the 9–5 workday with more adventurous, newer songs "baked into the mix" as the listener base skews younger at night.
Most radio formats are based on a select, tight rotation of hit singles. The best example is Top 40, though other formats country, smooth jazz, and urban, all utilize the same basic principles, with the most popular songs repeating every two to six hours, depending on their rank in rotation. Generally there is a strict order or list to be followed and the DJ does not make decisions about what selections are played.
AOR, while still based on the rotation concept, focused on the album as a whole (rather than singles). In the early 1970s many DJs had the freedom to choose which track(s) to play off a given album—as well as latitude to decide what order to play the records in.
Later in the 1970s AOR formats became tighter and song selection shifted to the Program Director or Music Director, rather than the DJ. Still, when an AOR station added an album to rotation they would often focus on numerous tracks at once, rather than playing the singles as they were individually released. As AOR stopped playing new music and died out in the late 1980s the core repertoire of AOR became that of the Classic Rock format.
Radio consultants Kent Burkhart and Lee Abrams had a significant impact on AOR programming. Beginning in the mid-1970s they began contracting with what would become over 100 stations by the 1980s. Lee Abrams had developed a format called SuperStars, pioneering it at WQDR in Raleigh, North Carolina, and had been very successful in delivering high ratings. The SuperStars format was based on extensive research and focused on the most popular artists such as Fleetwood Mac and the Eagles and also included older material by those artists. While his SuperStars format was not quite as tight as Top 40 radio, it was considerably more restricted than freeform or progressive radio. Their firm advised program directors for a substantial segment of AOR stations all over the US. This might be considered somewhat ironic, considering that the format’s origins were based on a free-form approach without playlists.
In the early 1980s, AOR radio was criticised for the lack of black artists included in their programming. AOR programmers responded that the lack of diversity was the result of increased specialization of radio formats driven by ratings and audience demographics. In 1983, the undeniable success of Michael Jackson's album Thriller led some AOR stations to soften their stance by adding Jackson's "Beat It", which featured Eddie Van Halen, to their playlists. At the same time other black artists also made inroads into AOR radio—Prince's "Little Red Corvette", Eddy Grant's "Electric Avenue" and "Beat It" all debuted on Billboard's Top Tracks chart the same week in April 1983.
The relative success of Michael Jackson's "Beat It" did not open the floodgates for other black artists on album-oriented rock stations. However, the door was cracked and through the remainder of the 1980s Jon Butcher, Tracy Chapman, Living Colour, Prince and Lenny Kravitz did manage to receive AOR airplay of varying magnitude.
Spin-off formats 
The phenomenal success of the album-oriented rock and the highly competitive battle for ratings likely contributed to the format splintering to reflect different stylistic perspectives. The 1980s saw some stations adding glam metal bands such as Mötley Crüe and Bon Jovi, while others embraced modern rock acts such as The Fixx, INXS and U2. But by the end of the decade, AOR stations were playing fewer and fewer new artists and the rise of grunge, alternative and hip-hop accelerated the fadeout of the album-oriented rock format. By the early 1990s many AOR radio stations switched exclusively to the classic rock format or segued to other current formats with somewhat of an AOR approach:
- Adult Album Alternative (known as Triple A) echoed a softer AOR without the hard rock or heavy metal. For a time Seattle's KMTT even promoted Freeform Fridays, and the Grey Pony Tail Special to highlight the halcyon days of FM radio. WXRT/Chicago is a long running AAA station. Other Triple A stations with strong heritage are KINK/Portland, Oregon and KBCO/Denver-Boulder.
- Modern Rock/Alternative: Pioneers in this format were KROQ-FM in LA and 91X (XETRA-FM) in San Diego, taking the AOR programming approach to music with New Wave, punk, college rock and grunge/alternative leanings, mostly in the 1980s. Today's KROQ and 91X are considered mainstream Alternative.
- Active Rock: Today's mainstream AOR, playing acts such as Stone Temple Pilots, Nickelback, Creed, Foo Fighters, Linkin Park and Korn. The active rock format was pioneered by the formerly broadcast (now internet only) "Pure Rock" 105.5 KNAC-FM out of Los Angeles, California in 1986. KNAC Program Director/DJ Tom Marshall and KNAC Music Director/DJ Michael Davis had previously worked at rock station KFMG/Albuquerque, NM. Active Rock or Hard rock was also pioneered by The Nationally Syndicated Z Rock Network (which lasted from 1986–1996) and expanded upon by WXTB-FM out of Clearwater, Florida starting in 1990.
AOR radio stations 
The radio stations in the following list were successful with the AOR format. In the 1970s some were considered progressive, with programming that evolved to what became known as AOR. Many of these stations have switched from AOR to another format—in some cases classic rock or one of the other AOR spin-offs mentioned above.
- Gent, George. "AM-FM Radio Stations Ready For the Great Divide Tomorrow" New York Times December 31, 1966: 39
- Scott, Jane. "Rock reverberations" The Plain Dealer November 28, 1975: Action Tab p. 26
- Peeples, Stephen. Rock Around the World March 1977: 21
- Goldstein, Patrick. "FM Radio: Redneck Rock?" Los Angeles Times September 21, 1980: T80
- King, Bill. "Burkhart Opens Doors To Suite and Format Secrets" Billboard September 23, 1978: 22
- Thompson, Bill. "As Formats Change, Cries of Bias Arise" Philadelphia Inquirer February 15, 1982: D1
- Heron, Kim and Graff, Gary. "Racism in the World of Rock/On Some Stations, Blacks Hardly Ever Make the Airwaves" Detroit Free Press January 9, 1983: 1C