[jrm4]

Nice.

Let me also put this idea out there that I've fantasized about (and basically just decided to make in "analog" by cutting up paper)

A thing that lets you enter multiple chords (like you might see on e.g. the guitar tab/chord site) and shows multiple rows of keyboards so that it's easy to see the progressions and exactly how each note moves.

Even with my "analog" version I really like how e.g. "Dm to F" doesn't naturally yet for me trigger any similarity, but when I look on my little pieces of paper, it's just like, oh, the D becomes a C and that's the only difference, and also it's easy to see the possible fingerings of multiple inversions.