I wonder how hard it would be to make tool that can take an existing audio file and digitally alter the frequencies in each section to give us a perfect just-intonation all throughout (by subtly lowering or raising the frequencies to form perfect ratios with other frequencies being played at the same time). You could even get this to run in real time on digital pianos, giving you perfect just-intonation depending on the chord or keys you play. The change in frequency would be unnoticeable alone but might be noticeable when played together with other keys, making the song more melodious.
