Leave it to Radiohead to come up with one of the most beguiling musical easter eggs we’ve ever seen. As Gizmodo notes, some intrepid Redditors discovered that the recent reissue of the band’s landmark 1997 album OK Computer contains a hidden computer program, designed to run on a vintage machine called a ZX Spectrum. And the code isn’t written out in the liner notes, or included on a USB drive, but embedded as audio within the music itself.

The deluxe box set edition of OKNOTOK contains what is described on Radiohead’s web store as a “C90 cassette mix tape compiled by the band, taken from OK Computer session archives and demo tapes.” Users on Reddit’s Radiohead board realized that the sound that opens the tape is the startup music from the ZX Spectrum, an ’80s 8-Bit computer from the UK that was used to create some sound effects on OK Computer’s “Let Down.” (Reddit also has a full tracklist for the cassette, if you’re interested.) From there, a Redditor realized that the end of the cassette contains an audio message designed to be fed into the Spectrum, which ran programs from cassette tapes. After some tinkering, another Redditor named Maciej Korsan got it working on a Spectrum emulator and uploaded the results to YouTube.

After some startup blips and bloops, the Spectrum displays the following message: “inside your home computer are… Thomas Yorke, Colin Greenwood, Jonathan Greenwood, Edward O’Brien, Philip Selway, Nigel Godrich, & Stanley Donwood. 19th December 1996. scroll?” The date on the program suggests it was created during the sessions for OK Computer.

After that, it’s a lot of bright 8-bit colors and even more blips and bloops for a few minutes. See the full video of the program below.

According to the Redditor who uploaded the video, the program’s code itself also contains a hidden message: “congratulations….you’ve found the secret message syd lives hmmmm. We should get out more.”

Syd, I’m guessing, is Syd Barrett, the late and troubled mastermind of Pink Floyd’s earliest material. As for whether the band should “get out more”–well, if they’re working on records as good as OK Computer, they can stay inside for as long as they like.

This article originally appeared on Spin.