Why does a piano sound like a piano?

The little details like sympathetic vibration and hammer sounds make a huge difference in realism. Particularly in making the player believe -- most sampled synths have an "uncanny valley" due to the absence of subtle cues like spatial effects, velocity detuning, and hammer damping. Pianoteq Stage is the first piano synth I've used where I don't immediately miss the acoustic piano I grew up with.