Stop me if you've heard this idea before... I am currently under the misguided impression that I just invented this!
Sampled pianos are already very realistic. Witness the Steinway in GPO... very nice indeed! The only thing they don't do, is account for sympathetic vibrations in the strings. On a real piano, hitting middle C sounds different with the sustain down than it does with it up, due to strings with overtones in common vibrating sympathetically. I had an idea for how to do this artificially, and rather than patent it and make a million dollars I thought I'd submit it to the public firing range.
THE SIMPLER VERSION
A piano with the sustain pedal down acts as a resonant chamber of sorts. Yell into an open lid with the pedal down, and you'll get a unique kind of reverb... one with equal-tempermant eq bumps (among other qualities). Question: can this be used as the basis for a reverb impulse? Assuming it could, imagine having this piano-ized reverb switched in and out of the mix, keyed to the sustain pedal (MIDI 64).
THE INSANE VERSION
Make an impulse for every note of the piano, and gate them with key down/up messages. This goes to the extreme of letting middle C sound different if the C an octave below is held, vs. if the F below that is held, etc. Since you'd need an impulse reverb for every note in your polyphony, this will probably have to wait until those 50GHz processors come out some time in the next 30 years.
Of course this all hinges on my question of whether an impulse taken of inside a piano would work the way I'm imagining it to. Anyone with the wherewithal to do such an experiment want to give it a whirl?
ps - If anyone DOES make a million dollars off of this idea, please send me lots of cool things. Thanks.