A new Kurt Cobain song is out Wednesday (April 8) -- 20 some years after Cobain's death. It doesn't appear to have a title -- and it's about as dark, beautiful and fleeting as the artist's life.

Today, Rolling Stone has an exclusive clip from HBO's upcoming documentary, "Kurt Cobain: Montage Of Heck," a gorgeously animated snippet featuring what director Brett Morgan said is a previously unreleased song that he found in a storage facility in 2013.

A whispery, acoustic track, the jam is more Nick Drake than grunge -- sweet and sad as opposed to outright angry.

The magazine also spoke with Cobain's daughter (and the documentary's executive producer), Frances Bean, about the doc and her relationship to the memory of her father.

"I was very specific about what I wanted to see, how I wanted Kurt to be represented," Frances Bean told RS of the film. "I told [Morgan], 'I don't want the mythology of Kurt or the romanticism.' Even though Kurt died in the most horrific way possible, there is this mythology and romanticism that surrounds him, because he's 27 forever."

And it seems she has achieved her goal. Watching "Kurt Cobain: Montage of Heck" feels a lot like trespassing. Watching someone else's home movies. Reading someone else's diaries. Looking through someone's things. Probably because that's exactly what it is: Looking, deeply, into a very public life that in some ways desperately wanted to be private.

Check out the track above and the documentary on HBO on May 4.