The Thumper of a Piano

A musical instrument's tone, or tamber, is largely shaped by the relative strength of each harmonic to fundamental frequency. This is why we've got lots of different instruments that can produce a c note - but they don't all sound exactly the same. We perceive these harmonics as collectively being a single sensation and so when you hit a c on a piano, what we're essentially hearing is that fundamental frequency of c. The idea is that harmonics that can even go above where the typical human can hear can still shape notes we do hear.