4. U2, 'Achtung Baby'
It was one of the most extreme personality transformations in pop music — ever. U2, the Irish bards of cathedral-chime guitar and pub-stool sermonizing, said goodbye to the Eighties and the suffocating tide of their own sincerity by setting up their recording gear in post-Wall Berlin and saying hello to the two i's: irony and industrial dance music. The music — slower than The Joshua Tree — is corrosive, razed-city funk laced with mad laughter and creeping paranoia. Yet the album's crackle and empty-hallway echo are really a kind of protective armor for the defiant heart in Bono's lyrics ("One," "Ultra Violet [Light My Way]") and the real lesson of Achtung Baby's postmodern giggles: To appreciate the joys of heaven, sometimes you have to take a little walk through hell.