As Radiohead fans are on high alert in anticipation of the band's upcoming ninth album, many in the U.K. just received a mysterious update in the mail with leaflets reading: "Sing a song of sixpence that goes/Burn the Witch/We know where you live."

In the enigmatic world of Radiohead, that's about as clear as communication gets and, along with other signs, it likely signals that the release of their highly anticipated album is imminent.

"Burn the Witch" refers to an unreleased Radiohead song that's at least 13 years old – the first mention of the track appeared in Stanley Donwood's art for 2003's Hail to the Thief. Two years later, "Burn the Witch" was written on a chalkboard with the song titles of potential tracks for 2007's In Rainbows. And, in 2007, Yorke posted the song's lyrics on Radiohead's website, including the line, "Sing the song of sixpence that goes 'Burn the witch.'"

Fans on Reddit have pointed out that, depending on the year, April 30 or May 1 is known as "Walpurgisnacht," or "Witches Night" in German lore. Sunday, May 1 also marks International Dawn Chorus Day, and Radiohead named their recent limited liability partnership "Dawn Chorus."

They'll kick off their 2016 tour on May 20 in Amsterdam and they'll head stateside in July with headlining performances at Lollapalooza and Outside Lands.

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