At the dawn of the 1990s, most of the biggest bands in the world – Def Leppard, INXS, Bon Jovi, Mötley Crüe, Poison – marched blindly into the new decade, releasing a watereddown retread of their last album. Not U2. Abandoning the stadium-size sincerity of LPs like The Joshua Tree, they went to Berlin, drew on krautrock and club music and created what Bono called "probably the heaviest record we've ever made" – a barrage of irony, distortion and still-huge hooks.

This deluxe box set features both Achtung Baby and its spacedisco follow-up, 1993's Zooropa, along with B sides, remixes, previously unreleased outtakes and a Kindergarten disc, basically an early version of Achtung Baby. The best of the unheard tracks may be "Down All the Days," an early version of "Numb" with Bono on vocals instead of the Edge. Others are more interesting than thrilling, like "Oh Berlin," a soaring ode to the birthplace of Achtung Baby, and "Heaven and Hell," a moody synth number with some unexpected doo-wop flavor. A few tracks on Kindergarten sound nearly identical to the final versions; others went through major restructuring: In its early form, "One" sounds like a campfire singalong. The bonus material is not essential listening, but since U2 rarely pull back the curtain on their creative process, it's fascinating to hear this rough draft of history.

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“Tonight's the Night”

The lead cut and title track from this girl group's debut album, "Tonight's the Night" was written by 19-year-old bandmember Shirley Owens, who sings lead, and producer Luther Dixon. The band from Passaic, New Jersey met in high school, first calling themselves the Pequellos. The song's frank thoughts about sexual and emotional surrender was racy for the time, but that didn't stop the Chiffons from cutting a similar version immediately after the original came out. "We were the first female group to write some of our own material," band member Beverly Lee recalls. "We did have some say-so in our writing."