The term "top 40" is also used to refer to the actual list of hit songs, and, by extension, to refer to pop music in general. The term has also been modified to describe top 50; top 30; top 20; top 10; hot 100 (each with its number of songs) and hot hits radio formats, but carrying more or less the same meaning and having the same creative point of origin with Todd Storz as further refined by Gordon McLendon as well as Bill Drake. The format became especially popular in the sixties as radio stations constrained disc jockeys to numbered play lists in the wake of the payola scandal.
Also known as CHR/pop or teen CHR. Plays pop, and dance, and sometimes urban, alternative, rock, and country crossover as well. Often referred as "top 40"; in terms of incorporating a variety of genres of music, CHR/pop is the successor to the original concept of top 40 radio which originated in the 1950s. WHTZ in New York City, KIIS in Los Angeles, KRBE in Houston, WIOQ in Philadelphia, WBBM in Chicago, WFLZ in Tampa/St. Petersburg, WHYI in Miami, WNCI in Columbus, WZPL, in Indianapolis, and KDWB in Minneapolis/St. Paul are the best-known CHR/pop stations in the U.S. See also: Mainstream Top 40 (Pop Songs)
These stations typically are hybrids of the contemporary hit radio (CHR/pop) and hot AC formats. This format contains a strong focus on current chart, contemporary and recurrent hits as well as placing a minority of older, classic hits from the 1990s and 2000s onto the playlist. Adult CHR stations play pop-friendly rhythmic, dance or hip hop titles from artists such as Rihanna, Beyoncé, Pitbull, Flo Rida, Britney Spears, Usher or Ne-Yo while still shying away from hardcore hip hop.
Examples in the U.S. include WKRQ in Cincinnati, WWMX in Baltimore, WKFR-FM in Kalamazoo, WWWQ in Atlanta, KVIL in Dallas-Fort Worth, WZYP in Huntsville, KBMX in Duluth, WMXZ in Charleston, Sirius XM Hits 1, WNDV in South Bend, WIXX in Green Bay and WARQ in Columbia, South Carolina. United Kingdom (UK) media regulator Ofcom states: "where a format requires a contemporary and chart music service, the main diet must be of modern music, reflecting the charts of today and recent months. Older, classic tracks would not be out of place, but only as spice to the main offering."
The adult CHR format is sometimes utilized by stations which are heritage Top 40/CHR outlets in their respective markets which have been in the format since the 1970s or 1980s or FM successors to former AM top 40s. See also: Adult Top 40, a US Billboard chart.