Classic rock radio operates on the idea — as we explored in Monday's piece — that if you ask people what they consider classic, they will tell you and you can play that. But Nirvana muddied the waters. So for the time being, if you want a timeline, classic rock is the stuff between The Beatles … … and Nirvana.

When did Nirvana become classic rock?

Their music maintains a popular following and continues to influence modern rock and roll culture. In the late 1980s, Nirvana established itself as part of the Seattle grunge scene, releasing its first album, Bleach, for the independent record label Sub Pop in 1989.

What's considered classic rock?

The classic rock genre encompasses rock music made over three decades, from '60s psychedelia and '70s album-oriented rock (AOR) to 1980s college rock, heavy metal, and 1990s grunge. Most classic rock songs are guitar-driven, and the genre has many guitar heroes—from Jimi Hendrix to Jeff Beck to Eddie Van Halen.