This may be too beyond audio cassettes, but I figured I'd share. I never really was interested in this portion of my first PDP-8 haul, but I ended up with a Tennecomp Fidelipac drive. For those unfamiliar, these were commonly used for commercial breaks in radio stations and the stations' jingles. Similar to 8-track, but they didn't have a built-in pinch roller. I have yet to see if the unit is functional, and need to figure out where the interface card is (if it came with the interface, even), as I would like to digitize the tapes. Fortunately, I've got a friend with some radio station cart machines, so I could possibly record them to audio files and reverse engineer them from there. So yes, even a PDP-8/M, ca. 1974, and possibly prior, used an audio tape system for data storage! Pictures here: https://photos.app.goo.gl/kBL9gRGF697A0xUT2 Kyle