One afternoon in April 1990, Kurt Cobain, Krist Novoselic and drummer Chad Channing arrived at producer Butch Vig's Smart Studios in Madison, Wisconsin, after driving 1,900 miles from Seattle nonstop. "They rolled up in a van," says Vig, "and they probably hadn't taken a bath or shower in three or four days."
The songs Nirvana began recording that day would eventually become Nevermind, the album that kicked off the alt-rock explosion of the Nineties. Eight of the demos from that week, including ferocious test runs through "In Bloom" and "Lithium," are among the never-before-heard treasures on the 20th-anniversary edition of the landmark album, due September 27th. The set, which will be available in versions ranging from a single CD to a five-disc box, was assembled by Novoselic, Dave Grohl, Vig and Nirvana's management, as well as representatives of Cobain's estate. Along with a remastered version of Nevermind, the multidisc packages offer killer extras including B sides, alternate mixes and an entire live show.
"We had this motel room, and we would go to Smart Studios and work every day," says Novoselic. The sessions were fruitful but not without difficulties. "Kurt was charming and witty, but he would go through these mood swings," says Vig. "He would be totally engaged, then all of a sudden a light switch would go off and he'd go sit in the corner and completely disappear into himself. I didn't really know how to deal with that." Although Nirvana's studio money ran out after five days, the demos they had recorded in that span were strong enough to score them a major-label deal a few months later.
In the spring of 1991, Nirvana – by then with Grohl on drums instead of Channing – regrouped in Tacoma, where they cut another batch of demos. "We were this transient band, crashing other bands' practice pads," says Novoselic. Whenever they found a place to play, they'd work on whatever Cobain brought in that day.
"Kurt was so compelled to write songs, so he'd always be banging something out," Novoselic adds. "He'd have these ideas, and we'd just kick 'em around for hours." They recorded the rehearsals on a boombox, and those rough tapes – including spellbinding sketches of "Smells Like Teen Spirit" and "Come As You Are" – are another highlight of the reissue package. "The boombox recordings are some of the coolest stuff for hardcore fans," says Vig. "They sound superlow-fi and dirty and trashy, really primal."
That May, the band met Vig in L.A. and began recording the versions that appeared on Nevermind. "We were really focused, no shenanigans or messing around," says Novoselic. "Every day, we'd go in around 11:00 or noon until 9:00 at night, just doing our thing." Vig remembers a more relaxed schedule: "They'd stay up all night and take drugs and go to the beach in Santa Monica, then wander in at three or four in the afternoon the next day. They were really enjoying a moment of freedom, and in the back of their minds, they knew they were making a great album. Those were fun times, man, before any of the craziness happened."
The band's first attempt at mixing Nevermind, though, was a disaster. "I'd be balancing the drums and the guitars," says Vig, "and Kurt would come and say, 'Turn all the treble off. I want it to sound more like Black Sabbath.' It was kind of a pain in the ass." They mutually agreed to bring in a hired hand, Slayer producer Andy Wallace, to do a final mix; the discarded, original mixes sat in a vault until the reissue.
Nirvana spent the weeks surrounding the album's September 24th, 1991, release on a whirlwind tour of Europe. "People were telling us that we were blowing up, and we were just like, 'Really?'" says Novoselic. The newly minted stars came home to Seattle's Paramount Theatre for a legendary Halloween '91 show that fans can hear for the first time on the deluxe reissue. "We were burned out," says Novoselic. "But it was a Halloween show, so we got pumped up and pulled it off."
Looking back, Novoselic sees that show as a turning point for Nirvana: "That was like the end of the innocent days. Then everything just got so huge, and it was hard to make that adjustment. I'm still trying to reconcile with all that."
Last fall, as the reissue was taking shape, Novoselic traveled to L.A. to play bass on a track for Foo Fighters' Vig-helmed album Wasting Light. Grohl, Novoselic and Vig sat around reminiscing for hours after the session was done. "We started pulling stories out of each other," says Vig. "It was a special night."
"It can definitely be emotional," adds Novoselic about those memories. "It's loaded with a lot of things. But if you just think about the music, that's what kept Nirvana together – we liked to play together, and we played together well. That was at the core of it, and that's what endures."
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This story is from the September 1, 2011 issue of Rolling Stone.