[bambax]

Yeah ok but MIDI files can be extremely complex, with different note lengths, timing, chords, etc. etc. It would be impossible to "play" on a web interface, only with a keyboard. And then it would just be Flowkey? -- or the app you are making...

That said, it's true that music is not random; learning to read actual music can be a plus over reading an arbitrary sequence of notes (although if you can read random notes fast, you probably also can read non-random music). It could also make sense for music teachers to upload a piece so that their students all work on the exact same music for example.

In that case the app could "flatten" any piece of music into a simple succession of quarter notes. It would not be very different from what it is today, though -- except less random. So, why not.