I played the saxophone for many years. Music has always been an interest of mine, but I have no application for it. Thus, my ear for progressions, pitches, intervals, etc. has waned. In spite of there being no clear end-game other than education (as in you can't "beat" it), this is the type of thing that I could do for hours on end.

I don't know the challenges involved (haven't seen the codebase), but you should package this into a Cordova or some other JS phone app. I'd download it in a heartbeat. I'd also be willing to assist if you needed extra hands.