Looks great! I like the idea of focusing on highlighted regions at a time. I spent some time exploring similar form factors for learning the fretboard, focusing intervals and shapes more than the notes themselves (link below) - I implemented a two-step drag-and-release gesture with visual feedback for selecting positions on a mobile device, and I think it helps avoid frustrating mis-taps. Maybe something to consider for your UI as well. The additional modules look interesting! Bookmarked.