Funny thing, I recently attempted exactly same thing, just as interactive toy. I had notes arranged in lattice (Tonnetz, harmonic table layout, however you wan

Funny thing, I recently attempted exactly same thing, just as interactive toy. I had notes arranged in lattice (Tonnetz, harmonic table layout, however you want to call it) with full chromatic range of 3 and half octaves. The lattice responds to touches by playing correct note. The patterns really become obvious on lattice layout. Major and minor chords are visually recognizable and harmonic shifts are just graphical translations due to lattice isomorphic properties. I extracted notes of Moonlight Sonata, and did simple analysis to determine how likely note M appears after note N (Markov chains). After few notes are played on lattice, the Moonlight Sonata analysis is used to suggest (highlight) some choices that could follow played notes. If you follow these suggestions, the Moonlight Sonata 'feel' is easily recognizable to listener. Player still has full control of tempo, composition structure and embellishments. It was meant to be an experiment into interactive music, sort of auto-complete embedded in musical instrument. Unfortunately the highlighting worked only in original key of composition (C#). When I tried to analyze intervals instead of absolute pitches, the suggestions became erratic and no longer musical. Also I found it hard to analyze and visualize polyphony. I might revisit this project and make it work in the future.