7. Led Zeppelin, 'Led Zeppelin II' (1969)
Their 1969 debut made it pretty obvious that these boys weren't just Jimmy Page's new heavy blues band. But at some point during the second album – during "Whole Lotta Love," maybe even from the guitar's first pelvic chug – you could hear the Seventies start. You could tell that this new decade was gonna be heavy, with riffs as much as melodies defining its spirit. And at some point during "Ramble On" – probably when Gollum steals Robert Plant's girl away – you could tell that this new decade was gonna get pretty weird.