I love the choice of a waltz for the ending of a game. You went for precision level 3 but I think, you would have hit the steampunk-era feeling better than most people who went for level 4 or 5.
I'd suggest splitting the instumentation into at least two instruments, like a piano and a harpsichord. Right now, it doesn't feel like an actual performance because there are more lines being simultaneously played than a single person could handle (and overall not enough to warrant a second person on the piano). A second instrument would help with keeping the illusion up, that this is not a virtual instrument but actual people performing.