I've played around with techniques like this too.

My thought was to make a multimedia tape zine where people could submit songs and accompanying short text. One track of a stereo cassette track would store the audio mixed to mono, the other would store the text encoded something like this. You'd play the tape in a cassette player outputing to a computer that would play one track to a speaker and decode the other to a thermal printer, so the text would also appear on a "tape."

The problem is, it's really hard to find working cassette players with stereo input and output...