According to NME:
The Nirvana Box will be a four-disc set and “will feature 81 tracks including 68 previously unreleased recordings – rehearsals, outtakes, Kurt’s home demos, as well as a DVD which is confirmed to have unreleased band home movies, live footage, rehearsal footage and 20 full-length video performances. A 60-page booklet will accompany the release.”
A source told NME.COM: “I’ve seen some of the footage and it’s amazing stuff. There’s a video of them performing at a friend’s party with Kurt reading lyrics off a sheet of paper on the wall, footage of them covering ‘Seasons In The Sun’ in a studio with Kurt on drums and lots of other great stuff.”
