How Does a Piano Make a Sound?

Curator
5 days ago
2 min read

Every note you hear from a piano is the end result of a short chain reaction: a key press turns into a hammer strike, the hammer strike sets a string vibrating, and that vibration gets amplified into the sound that fills the room. Here's how each step actually works.

1. The key press triggers a hammer

Pressing a piano key sets off a small mechanical lever system called the action. The key lifts an assembly that launches a felt-covered hammer toward the string above it — the harder you press, the faster the hammer travels, and the louder the resulting note. This is the same basic hammer mechanism Bartolomeo Cristofori invented around 1700 to let players control volume, something the earlier harpsichord couldn't do.

2. The hammer sets the string vibrating

The hammer strikes one, two, or three strings (depending on the note) and immediately springs back out of the way, letting the string vibrate freely. A string's pitch comes down to three physical properties: length, thickness, and tension — longer, thicker, looser strings vibrate more slowly and produce lower notes, which is why a piano's bass strings are so much longer and heavier than its treble ones.

3. The vibration passes through the bridge

On its own, a vibrating piano string barely makes a sound — it's too thin to move much air. To get from "vibrating wire" to "sound that fills a room," that vibration has to travel through a bridge: a strip of wood glued to the soundboard that the strings press against.

4. The soundboard amplifies it

The bridge transfers the string's vibration into the soundboard — a large, thin wooden panel (usually spruce) stretched beneath the strings. Because it has so much more surface area than a string, the soundboard can push a lot more air, turning a faint vibration into an audible tone. This is the principle of resonance: the soundboard vibrates at the same frequency as the string and amplifies it dramatically, the same way an acoustic guitar's body amplifies its strings.

5. Overtones give each note its character

A struck string doesn't just vibrate at one frequency — it vibrates at its fundamental pitch and a series of higher overtones simultaneously. The mix of these overtones is what gives a piano its rich, complex tone, and why the same note sounds different on different instruments; a Steinway and a Bösendorfer produce different overtone blends from the same physical soundboard principle.

6. The damper stops it

When you release the key, a felt-covered pad called the damper falls back onto the string, stopping the vibration and ending the note. Press the sustain pedal, and the dampers lift off every string at once, letting notes ring on and even letting other strings resonate sympathetically with whatever you're playing — part of why the sustain pedal makes a piano sound so much fuller.

The same physics, three centuries of instruments

This chain — hammer, string, bridge, soundboard — is the shared thread running through every piano in our catalogue, from Cristofori's earliest 18th-century instruments to 19th-century concert grands. Browse our collection of historic keyboard instruments to see how different makers and eras put their own spin on this same basic mechanism