A previously unheard Kurt Cobain acoustic song is to appear on the soundtrack for the forthcoming documentary, Montage Of Heck.

Writing on Twitter, the film’s director Brett Morgen said: “Listening to a mind blowing 12 minute acoustic Cobain unheard track that will be heard on the montage of heck soundtrack.”

Morgen, whose previous credits include the Rolling Stones’ documentary Crossfire Hurricane, debuted Montage Of Heck at the Sundance Film Festival in January. The film will be released in the UK on April 10.

Speaking to Rolling Stone, Morgen revealed that the score for the documentary consists of “unreleased Cobain music.

“They don’t have titles. Before people saw the movie, there were these weird press releases focusing on the unreleased music. And it’s like: It’s a movie. We’re not going to stop it and play a song for four minutes,” Morgen said. “But nobody in Kurt’s life — not his management, wife, bandmates — had ever heard his Beatles thing [a snippet of ‘And I Love Her’]. I found it on a random tape. It’s a Paul [McCartney] song. How’s that for shattering the myth?”