Grand piano actions/mechanisms are complicated and occasionally need a "regulation" or adjustments to ensure everything works perfectly. as originally designed.
The action of a grand piano is a complex mechanism that allows the piano to produce sound when the keys are pressed. It translates the motion of pressing a key into the movement of a hammer striking the strings to produce sound. Here's a step-by-step and video overview of how a grand piano action works:
Key Press: When a pianist presses a key on the keyboard, it sets the action in motion. Each key is connected to the action via a system of levers and pivots.
Key Levers: The key press activates a series of levers, starting with the key lever. When the key is pressed down, the key lever moves upwards.
Jack and Escapement: Connected to the key lever is a part called the jack. When the key is pressed down, the jack is lifted upwards as well. The jack has a small "tongue" or "flapper" that reaches upward, ready to engage the hammer.
Repetition Lever: The repetition lever is a crucial part of the grand piano action, ensuring that the key can be played rapidly without fully returning to its resting position. When the key is pressed down, the repetition lever is also lifted.
Damper Mechanism: At the same time, when the key is pressed, the dampers (felt-covered strips) that rest on the strings are lifted, allowing the strings to vibrate freely when struck.
Hammer Lifting: As the key lever and jack rise, they lift the hammer along with them. The hammer is mounted on a separate part called the hammer shank.
Escapement and Catch: As the key continues to be pressed down, the jack reaches a point where it disengages from the hammer's tongue. This moment is known as the escapement. At the escapement point, the repetition lever catches the jack, allowing the pianist to repeat the note without lifting the key fully.
Hammer Release: After the escapement, the jack is allowed to drop back to its original position under the control of the repetition lever. Meanwhile, the hammer is left suspended at a specific distance from the strings, determined by the key's position.
String Strike: When the key is released, the action moves in the opposite direction. The hammer, now under the force of gravity, is driven towards the strings. As it strikes the strings, the strings vibrate and produce sound.
Dampers Return: When the key is released, the dampers return to rest on the strings, stopping the sound from continuing.
Repetition: If the key is pressed rapidly, the repetition lever will allow the hammer to catch the jack again after the escapement, enabling the pianist to play the same note rapidly without lifting the key fully.
The entire process is intricate and precise, allowing for the rich and expressive sound that a grand piano is known for. It's essential for the piano action to be well-maintained to ensure the piano remains in optimal playing condition.