The English rock band Radiohead has decided to sell some of its unreleased recording materials after a hacker stole them and threatened to leak them in an extortion scheme.

The proceeds will go toward Extinction Rebellion, an environmentalist movement that relies on nonviolent resistance to generate awareness and advance its causes.

In a tweet today, Radiohead guitarist and keyboardist Jonny Greenwood said a hacker last week stole lead vocalist Thom Yorke’s minidisk archive, which contained recordings from around the time of the band’s 1997 studio album, OK Computer. Reportedly, the hacker threatened to publish the materials if he (or she) did not receive $150,000.

“So instead of complaining – much – or ignoring it, we’re releasing all 18 hours…” Greenwood said in the post, which was retweeted by the official Radiohead Twitter account.

For just 18 days, the band is making the sessions available via the online music service Bandcamp for a price tag of £18. “So for £18 you can find out if we should have paid that ransom,” joked Greenwood.

“Never intended for public consumption (though some clips did reach the cassette in the OK Computer reissue) it’s only tangentially interesting,” Greenwood continued. “And very, very long. Not a phone download. Rainy out, isn’t it though?”

A brief product listing on the Bandcamp website, apparently written by Yorke, describes the materials as “my archived mini discs from 1995-1998(?). Yorke added: “it’s not v interesting” and there’s a lot of it.”

“[A]s it’s out there it may as well be out there until we all get bored and move on,” Yorke concluded.