Though there were rumours that he was planing a solo album before his death over 21 years ago, Kurt Cobain’s recorded output amounts to little more than three incendiary albums as frontman of Nirvana.

However, the director of Montage of Heck, the new documentary about Cobain, says that this could soon change.

Brett Morgen, who combed through over 200 hours of Cobain’s home recordings when researching his film, has compiled an album’s worth of “unreleased gems” to be released this summer.

He told US publication Bedford + Bowery that the “amazing” record “will feel like you’re kind of hanging out with Kurt Cobain on a hot summer day in Olympia, Washington as he fiddles about. It’s going to really surprise people.

“Just to be clear, it’s not a Nirvana album, it’s just Kurt and you’re going to hear him do things you never expected to come out of him.”

The tapes include a rough recording of Cobain covering the Beatles’ And I Love Her, which was distributed on the web last month.

Montage of Heck is broadcast on HBO in the US on 4 May.