I was thinking, in a world without DRAM, cobalt-infused magnetic tape (like that used for VHS and ferricobalt cassettes) or metal particle tape, digital sound recording would still be possible using 1960s black-and-white VTRs that took ferric oxide tape not dissimilar to those used for analog multitrack recording.

Cool project.

Though if you are looking at QR codes for something like this (internal, on paper), strongly consider using data matrix codes. They are more compact, same available error correction codes, and actually have a composition story rather then spaces between them.

Do to how datamatrix codes can be composed, you could probably design a code that both fills the height and does a continuous stream of codes with no horizontal white space between them, just a solid bar as per the spec.

Dolby have been doing this for years for audio on cinema film reels - literally from tiny QR-like codes between the sprocket holes on the filmstrip, with cinema-grade audio quality.

In a sense this is reinventing digital sound-on-film, but without the continuous feed and with a much lower tape speed. https://en.wikipedia.org/wiki/Sound-on-film

The compression choice is what makes this work. OPUS at 12 kbps is good enough to not embarrass itself — ten years ago you'd have needed a much faster tape speed to get acceptable audio. The paper tape is the aesthetic, the codec is doing the real work.

Has anyone yet made an app that lets you wave your phone around a vinyl record and capture macro video and then play the music through the phone's speaker?

Really like it. For some reason I'd insist on spectrograph instead of qr - artifacts make the medium. The fragile bizarre distortions and loss of the double digitization of analog data - you'd end up with more of an instrument than a format.

Think along these lines https://youtu.be/Z7Zb4rso82M?si=3FYaidCwwVdUhocO

Imagine being able to control where the loss happened in real time with potentiometers

Optical sound: https://en.wikipedia.org/wiki/Optical_sound