We all know that Nirvana frontman Kurt Cobain had more than his share of problems, according to 'Nevermind' producer Butch Vig -- being a pain in the ass was one of them.

With it's 20th birthday just around the corner, a lot of press is being focused on Nirvana's classic album 'Nevermind'. Rolling Stone caught up with the albums producer, Butch Vig, to talk about the recording process. Vig recalled that it wasn't the easiest recording session:

"I’d be balancing the drums and the guitar 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. Kurt was charming and witty, but he would go through these mood swings. 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."

Vig recently reconnected with Nirvana's Dave Grohl and Krist Novoselic as he produced the Foo Fighters album 'Wasting Light', which Novoselic guested on. The three sat around for hours reminiscing about the old days after they were finished working on the album. Novoselic says he still has mixed emotions about walking down that stretch of memory lane:

"It can definitely be emotional, 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."

The deluxe edition of 'Nevermind' is set for release September 19th.