Resonance

If you hold the sustain pedal down on the piano, open the piano lid and sing starting at a low pitch and slowly move up to a high pitch, one of the pitches is likely to resonate with the piano’s soundboard. It almost feels like the piano sings back to you.

Acoustic resonance is when the soundboard in the piano sympathetically vibrates with a sound wave. Every piano resonates at a different frequency, based on the texture of the soundboard, the shape of the piano, and other factors.

An obvious parallel between humans and resonant pianos: each of us “vibrate” and respond to a different frequency. And the only way to find that frequency is to try out a lot of different pitches.