[cracoucax]

Never used a BBC but 8bit computers of this era often used cassettes to load and save data.

The tape would contain bleeps and blurps which would be decoded into bytes by the computer. EG this is the sound produced by an Amstrad cpc464 loading a game: https://www.youtube.com/watch?v=OvChkOHgDIo

This meant that to copy software you didn't even need a computer, just a double cassette deck.

And that by recording the credits of this BBC show to tape and playing that back into the computer you'd load some program. That's actually a brilliant idea, I wonder what kind of software they broadcasted.

[vram22]

Yes, brilliant.

Sounds (pun not intended but noticed) like steganography.

https://en.m.wikipedia.org/wiki/Steganography

[vram22]

Got it, thanks.