Author here: Thank you so much for posting the article, I really appreciate it! The article actually began as a technical deep-dive into the internals of the Yamaha TX81Z. It seems as though most of the technology in the TX81Z is pretty well understood at this point. However I'd never seen anyone ever talk about how the cassette interfaces on the Yamaha synths actually worked. Figuring this out turned out to be way more fun than doing a deep-dive into the whole synth, and I got to learn a lot in the process. I know some people would definitely have already known how this worked. In my case, the synth is actually older than I am! I unfortunately missed out on the very interesting era of computing where this kind of technology was more common.