Also the "Muto Music Method": it's not just that the common keyboard finger positions aren't the same in 12 different scales, the notation could also be made without all these # and "b" (sorry HN filters out the flat sign U+266D from the text) and without the shapes of the melodies changing:

https://muto-method.com/en/issue.html

"The problems with 5 line notation"

I've found the page thanks to user mkl mentioning Chromatone keyboard here.