Modern rock is an umbrella term used to describe rock music that is found on college rock radio stations. Some radio stations use this term to distinguish themselves from classic rock, which is based in 1960s–1980s rock music. Radio format Modern rock (also known as alternative radio) is a rock format commonly found on commercial radio; the format consists primarily of the alternative rock genre. Generally beginning with Hardcore punk but referring especially to alternative rock music since the 1980s, the phrase "modern rock" is used in the US to differentiate the music from classic rock, which focuses on music recorded in the 1960s through to the early 1990s. A few modern rock radio stations existed during the 1980s, such as KROQ-FM in Los Angeles, XETRA-FM in San Diego, WHTG-FM (now WKMK) on the Jersey Shore, WLIR on Long Island, WFNX in Boston, and KQAK The Quake in San Francisco. Modern rock was solidified as a radio format in 1988 with Billboards creation of the Modern Rock Tracks chart. The chart was based on weighted reports from college radio stations and commercial stations such as those listed above. The 1988 episode of the VH1 show I Love the '80s discussed INXS, The Cure, Morrissey, Depeche Mode, and Erasure as modern rock artists representative of that year. But it was the breakthrough success of the grunge bands Nirvana and Pearl Jam in 1991 that resulted in many American radio stations switching to the format. Modern rock is considered by some to be a specific genre of alternative rock. The format has gone through two distinct periods, dividing the line from classic modern rock and the current alternative rock format used today. Up until grunge went mainstream, the format featured a wide variety of up-tempo danceable music from a diverse group of artists that were being played in rock discos and clubs. This was a legacy from new wave music and the Second British Invasion that immediately preceded it. Of all the artists who had songs hit the top 30 in the first modern rock chart, only seven of them were American. Between 1992 and 1994, most of the female, foreign and dance music had largely disappeared from the chart. While the chart still featured a variety of alternative rock music, it was largely guitar rock created by male Americans. By 1996, the modern rock chart was largely identical to the mainstream