As the release date gets closer for the 20th-anniversary editions of Nirvana’s ‘Nevermind,’ some of the album’s key figures have been sharing their memories about the sessions and the band’s frontman, Kurt Cobain.

Producer Butch Vig admits not knowing how to deal with Cobain’s mood swings when the band was recording demos of ‘Lithium’ and other eventual ‘Nevermind’ tracks at Vig’s Wisconsin studio in spring 1990.

“Kurt was charming and witty,” Vig recalls. “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.”

The following spring, Nirvana was in Los Angeles recording ‘Nevermind’ with Vig, who says the band members would “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.”

Nirvana bassist Krist Novoselic, however, recalls his band having a different and more regimented work ethic.

“We were really focused, no shenanigans or messing around,” Novoselic says, adding that the band usually worked in the studio from around noon to 9 p.m.

Those spring 1990 demo recordings Nirvana made with Vig, dubbed the ‘Smart Studios Sessions,’ will be included on the ‘Super Deluxe Edition’ of ‘Nevermind,’ which along with the other 20th-anniversary editions is due Sept. 27.