In July 1964, the U.S. Federal Communications Commission (FCC) adopted a non-duplication rule prohibiting FM radio stations from running a simulcast of the programming from their AM counterparts.
Programmers like Tom Donahue at KMPX in San Francisco developed stations where DJs had the freedom to play long sets of music, often covering a variety of genres.
Not limited to hits or singles, DJs often played obscure or longer tracks by newer or more adventurous artists rather than those heard on Top 40 stations of the day.
[7] WPLJ's parent company, ABC, installed similar formats on all of its FM stations, including KLOS in Los Angeles and WRIF in Detroit.
In 1972, Ron Jacobs, program director at KGB-FM in San Diego, began using detailed listener research and expanded playlists in shifting the Top 40 station toward a progressive rock format.
Meanwhile, at competing station KPRI, program director Mike Harrison was similarly applying Top 40 concepts to the progressive format, which he dubbed "album-oriented rock.
"[9][10] In the mid-1970s, as program directors began to exert more control over what songs played on air, progressive stations evolved into the album-oriented rock format.
However, program directors and consultants took on a more significant role in song selection, generally limiting airplay to just a few "focus tracks" from a particular album and concentrating on artists with a more "commercial" sound than those featured a few years earlier.
[15] While AOR had once championed soul, funk, and R&B artists like Stevie Wonder, War, and Sly Stone, the format no longer represented these styles and took a stance against disco.
The best example is Top 40, though other formats, like 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 the rotation.
AOR programmers responded that the lack of diversity was the result of increased specialization of radio formats driven by ratings and audience demographics.
At the same time, other black artists also made inroads into AOR radio: Prince ("Little Red Corvette"), and Eddy Grant ("Electric Avenue") debuted on Billboard's Top Tracks chart during the same week in April 1983.