Yeah, sorry, I took one look at this keyboard layout and thought to myself "ok this is a toy"

I'd love to see an application that could capture audio from an instrument and act as a real-time theory aid/teacher. For example:

  * the note you are playing is this
  * the notes you've just played in sequence belong to these scales. here are possibilities for next notes
  * try these chords
  * the chord you've just played is comprised of these notes
  * the next chord in the scale could be this
  * popular songs with these chords or in this scale are