With the 20th anniversary of Nevermind imminent, Nirvana mania has been reaching fever pitch of late. Of course, it wouldn’t be an anniversary without a massive record company cash-in celebratory box set, and sure enough, there’s a super deluxe box set out next week. Among other things, it contains a bunch of previously unreleased tracks, and now three of those tracks have appeared online. There’s an early version of “Breed” from the Smart Studio Sessions (the early sessions for Nevermind, with Chad Channing on drums), along with a “boombox demo version” of “On a Plain” and a live version of “Smells Like Teen Spirit” from the Paramount in 1991. Click here to listen, and let us know what you think — fascinating historical documents, or the sound of the bottom of the barrel being scraped? [Via Stereogum]