I have not, no. The above is kind of just random nerd knowledge I have from being a musician and having friends who play the piano.

In principle, I don’t see why you couldn’t just tune one of the notes with a regular tuner, and then tune all the rest relative to it, according to equal temperament. The most complex part about that would be the UI, to explain to the user which keys they have to press when.

But yeah, maybe I’m missing something hugely important about the process, for which you need all those fancy graphs that are shown in the app screenshots…