I can actually confirm that dropping a piano makes the characteristic BOOOOOONG sound that we all know. I’m not sure if they actually dropped a few pianos to record it… But I have personally dropped a piano off a ~10’ drop, (and was in the room when a second piano got dropped ~6’) and it sounded exactly like what you’d expect.

All of this is to say that if they didnt drop a piano, (because that’s risky and very expensive just for a sound effect), those foley artists were really fucking good at their jobs.