A previously unheard song will be among the 70 tracks included on the three-disc deluxe 20th anniversary reissue of Nirvana's final studio album, In Utero, which is set for release on September 24th. The song, called "Forgotten Tune," is an instrumental that was recently unearthed and has never been released in any form before. The rest of the material on the jam-packed set will consist of remastered, remixed, rare and unreleased demos, B-sides, alternate takes and live recordings. According to Rolling Stone, the set will feature two versions of the 12-song album: one will be a remastered version of the original disc, while the other will a newly remixed edition. It is not clear whether producer Steve Albini's more raw mix of the record will be included, but mixes he did of at least two songs -- "Heart Shaped Box" and "All Apologies" -- will be officially released as part of the set after years of bootlegging. Other rarities, non-album tracks and B-sides that will appear include "Marigold," "Moist Vagina," "Gallons Of Rubbing Alcohol Flow Through The Strip," "I Hate Myself And Want To Die" and "Sappy." The second of the three discs will feature demo versions of at least eight songs from In Utero, as well as Dave Grohl's 1990 demo of "Marigold," which was his first-ever solo recording. Also included will be Cobain's handwritten lyrics, a four-page letter Albini wrote the band spelling out his plans for the In Utero recording sessions, plus liner notes by comedian Bobcat Goldthwait, who opened for the band at some of the shows on its In Utero tour.