What Is A Piano's "Action?" | Piano Buyer's Guide
Érard's Excellent Invention
The mechanism of the piano that drives the hammers to strike the strings when a key is pressed is called the "action."
When speaking about the history of the piano action, one ought to reference the repetition mechanism, or double escapement, invented by Sébastien Érard of France. This mechanism allows the pianist to repeat a note in quick succession without having to fully release the key. Up until the introduction of this repetition mechanism, when a key was depressed, the hammer usually rose and struck the string and was not ready for the next keystroke, until it had gone back to its at-rest position. Erard's invention made it possible to prepare for the next keystroke even though the hammer hadn't completely made it back to its at-rest position.
Modern Action
It is said that Erard demonstrated a prototype of this mechanism for Beethoven in 1803, and this inspired the composer write new works. This mechanism has also been improved in a more refined form in today's modern actions.
Look closely at the movement of the levers. The hammer rises up only partway through its full movement. This allows it to respond correctly and produce sound, even when played numerous times in succession. Technically, the key can be played a maximum of 15 times per second.
Muting the Sound Is Also Important
The damper mechanism is also an important part of the action. This is the part that quiets the sound as soon as the finger is lifted from the key. In the photograph to the right, the four white parts are the damper felts. When the finger is lifted from the key, the dampers touch the strings from above thus stopping the strings from vibrating. Attached to the bottom of the long vertical wire is a damper weight
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