The line between alternative and mainstream rock was especially blurry in the ’90s. Chalk that up first to Nirvana: The Seattle trio shook commercial rock out of its doldrums and brought underground punk into the spotlight with their gleefully noisy 1991 major-label debut, Nevermind. However, it’s clearer today how much the ’90s modern-rock explosion owed to traditional classic rock. Grunge-associated artists such as Pearl Jam, Alice In Chains, and Soundgarden took cues from Led Zeppelin’s blues-oriented heft; mischievous punks Green Day loved more melodic British Invasion fare such as The Beatles and The Kinks. In hindsight, it's also no wonder so many veteran bands connected with a younger generation of fans. Seventies rockers Aerosmith and Tom Petty embraced big-budget MTV videos and vibey, laidback folk-rock, respectively, while ’80s-era bands favored reinvention: Metallica polished their trademark thrash into menacing hard rock on their blockbuster 1991 self-titled album, and both R.E.M. and U2 toyed with new sounds and slippery identities.