We can only await the revival of keyboard tuners, and the interviewees of the future puzzling over how many of them are required for a city the size of Chicago.

It's also not clear how you would handle keys that are held down. Or rather, how you would distinguish between keydown and keyup events. But perhaps with your tensioned wire you could use a pick on the key (such as in a harpsichord) which has a different texture on each side, affecting the timbre but not the pitch.