The Grand Piano Action is the mechanical assembly which translates into the depression of the piano key into rapid motion of a piano hammer, which thereby creates sound by striking the piano string. This entire process, which takes place when depressing the piano key, is described below in step by step detail. You can click on the graphic illustration above to open a larger picture showing the piano action numbered parts.
The piano key top (58) is depressed by the pianist’s finger. As the back of the key begins to rise, the capstan and capstan screw (42) pushes upward against the wippen cushion (41) which in turn raises and lifts the wippen (24). The wippen is hinged on the wippen flange (39), which is attached to the wippen rail (40). As the wippen is lifted by the key, it raises in turn the jack (31) and the repetition lever (19), which work together to begin to push the hammer (6) up towards the string (1). The jack and repetition lever push up on the hammer knuckle (20), which raises the hammer shank (7) and the piano hammer (6). The piano hammer (6) rotates on the hammer flange (9), which is attached to the main action rail (10). When the key (45) is halfway down, the damper lever key cushion (37) on the back of the key (45) begins to lift up the damper lever (36), which in turn raises both the damper wire block (12) and the attached damper wire (5). The damper wire block and the damper wire work together to lift the damper head (2) off of the string (1), which allows the string to vibrate and sound freely. When the hammer (6) is one-sixteenth of an inch away from the string, the top of the repetition lever (19) comes into contact with the drop screw (8), which stops the upward motion of the repetition lever. At this exact same moment the jack (31) comes into contact with both the let-off button punching (30) and the let-off button (29), which is attached to the let-off rail (28). The let-off button (29) causes the jack to rotate out from beneath the hammer knuckle (20), at this point, the hammer continues to move towards the string on its own inertia; it is no longer in contact with any other part of the action. This whole process is called single escapement, and this process is what allows the piano hammer to rebound immediately from the string while the piano key is still depressed. Without escapement, the hammer would be held against the string (stopping its vibrations) for as long as the key was depressed.
After the initial escapement, the key is completely depressed and the piano hammer head strikes the string – only to immediately rebound and have the hammer tail, which is the slender bottom part of the hammer, (6) be caught by the backcheck (15), which is attached to the back of the key by the backcheck wire (38). As the hammer rebounds to its original position, the hammer knuckle (20) forces the repetition lever to rotate downward on the repetition lever flange (18), causing the combination jack spring and repetition lever spring (23) which is attached to the bottom of the repetition lever (19) to compress. As the key is being released, the hammer is released by the backcheck, and the repetition lever spring pushes up on the repetition lever and raises the hammer. As the hammer is pushed upward, the jack (31) returns to its original position beneath the hammer knuckle (20). This resetting of the action is known as double escapement. The advantage of the double escapement action is that the action is reset without the key having to be completely released, which allows for much faster note playing repetition. If the key is completely released, the action parts resume their original at-rest positions. The hammer falls back onto the hammer rest (16), which is attached to the end of the wippen (24). The repetition lever button (21) stops against the wippen and returns the repetition lever (19) to its rest position, and the jack regulating button (25) is stopped by the wippen spoon (22), which is also attached to the top of the wippen (24). The entire grand piano action assembly is supported by both the back rail (48) and the balance rail (51) which is attached to the action bracket (32).
This entire process and the sequence of events that are described here – when the piano key is depressed by the pianist’s finger – must take place within the amount of time required to perform a staccato note. A good quality grand piano should be able to repeat this process up to eight times each second. Below is a video showing the Grand Piano Action in motion.
Greetings to Everyone and A Big Welcome to Infinity Music Studio! My name is Suzanne Brittania. I have been teaching piano and voice lessons for over 40 plus years. It is my hope that you will find all the following information, along with the music videos listed within my blog, to be very interesting, helpful and inspiring all throughout your own musical journey.
The videos listed below are of famous opera stars (that I performed with extensively all throughout my earlier musical career) especially during the 1950's and 60's.
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