A previously unheard NIRVANA track will take pride of place in the 20th anniversary edition of the band’s last album In Utero.

It’s to be one of more than 70 numbers which will appear alongside unheard alternative mixes, demos and more.

High points include a brand-new mix of the original album, Curt Cobain’s handwritten lyrics, a four-page letter from producer Steve Albini to the band, discussing his plans for the project, and a newly-mastered recording of the band’s Live And Loud concert in Seattle in 1993.

Universal Music Group say: “In Utero was the sound of the most incredible yet conflicted band of the era at the peak of its powers, coming to terms with a generational spokesband mantle they’d never seen coming – and ultimately surmounting these struggles to make the record they needed to make.

“As Rolling Stone’s David Fricke said in his review at the time, ‘In Utero is a lot of things-brilliant, corrosive, enraged and thoughtful, most of them all at once. But more than anything, it’s a triumph of the will.’”

The 20th anniversary In Utero will appear in a number of formats on September 23.