Grades 3–5 · Machines
How does a piano key make a hammer strike a string?
A piano key does not pull its string. Pressing the key moves a set of levers called the action. These parts lift a felt-covered hammer toward the string. The energy starts with the player’s moving finger and passes through the mechanism.
In the diagramA piano action strikes, releases and damps a string1. Press keyLevers lift2. Free hammerStrike, thenrebound3. Let key upDamper stopsthe vibrationEscapement frees the hammer before the strike.The free string keeps vibrating after contact.Simplified one-key action; sustain pedal unused.
Just before the strike, a part of the action lets the hammer move freely. This release is called escapement. The hammer hits the string and rebounds, leaving the string free to vibrate. A hammer held against the string would interfere with that movement. Vibration passes through the bridge to the soundboard, which moves surrounding air.
On a string with a damper, pressing the key also lifts the damper away. When the key is released, the damper returns and takes energy from the vibration, shortening the sound. The sustain pedal can hold dampers away even after fingers leave the keys. With the pedal unused, the action links each key’s movement to both the start and the end of its string’s sound.
About this explanation
Starting knowledge: Understand levers, vibration and energy transferred by a moving object.
Sources
- Yamaha — What is a Piano’s Action?
- Yamaha — The Sound-Producing Mechanism