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.
Upright piano action: upright piano internal operation.
Felt: cloth surrounding the hammer.
Hammer: piece that hits the string to make it vibrate.
Hammer rail: hammer support when it is not operated.
Catcher: piece that catches the hammer tail when it falls.
Back check: piece that catches the hammer tail when it falls.
Key: part of the keyboard that is pressed to produce a note.
Wippen: piece to which the strings are attached and that transmits the sound to the soundboard.
Jack: piece that sends the hammer head towards the string.
Hammer butt: part of the hammer that is pushed by the jack.
Spring rail: support for the damper when it is not operated.
Damper: piece that prevents the string from vibrating.
String: part of the piano that produces the sound by vibration when hit.
When a piano key is depressed slowly, it rocks on the center rail and goes up in back. The key raises the sticker and wippen. The wippen pushes the jack, which pushes the hammer butt. The hammer butt pivots on its flange and moves the hammer toward the string. When the key is half way down, the spoon engages with the damper lever, lifting the damper off the strings. When the hammer is almost to the strings, the jack heel bumps into the regulating button, and as the wippen keeps going up, the jack pivots and slips out from under the hammer butt. The hammer continues under its own inertia to the string, instantly rebounding.
At this point the strings start vibrating, the vibrations are carried to the bridge which transmits the vibration to the soundboard (the large, thin wood piece you can see in the back of the piano) which amplifies the sound (like a big speaker).
The catcher is caught by the back check and held in this position as long as the key is depressed.
When the key is released, the wippen drops, the back check releases the catcher, the briddle tape gives a little tug on the hammer butt, and with the help of the butt spring, the hammer returns to the hammer rail. The damper spring returns the damper to the strings, and the jack spring returns the jack under the butt, ready for the next repetition. This entire sequence occurs in a fraction of a second, allowing the pianist to repeat notes rapidly.
Tim Hendy demonstrates, in the video below, how the modern upright piano action works. Using a full scale working model, he demonstrates the actions of the key, hammer, damper, damper rest rail, balance hammer, check, lever and jack, concluding with concise recommendations for piano maintenance.
Most pianos, especially your modern pianos have three foot pedals. These foot pedals are called, from the left to the right, the 'Una corda' (or Soft) Pedal, the 'Sostenuto' Pedal, and the 'Damper' Pedal. Directly above is a picture showing the three foot pedals that are on a piano with each pedal having been labeled.
GRAND PIANO PEDALS
Una corda: The pedal on the left-hand side is also referred to as the 'Soft' pedal. On a grand piano, applying the una corda pedal normally shifts the entire keyboard (sideways) slightly over to the right, so that the piano hammers can strike only one or two of the two or three strings that are assigned to each note. The effect is a softer tone being played since fewer strings are being struck.
Sostenuto: This is the middle pedal and is the least used when playing the piano. The sostenuto pedal sustains only those notes which are being held down when the foot pedal is depressed, allowing future notes that are played to be unaffected.
Damper: This pedal is also called the 'Sustain' pedal. It is the right pedal on the modern piano. When applied, this pedal raises all of the dampers off the strings allowing them to continue to vibrate and sound even after a note on the keyboard has been released.
UPRIGHT PIANO PEDALS
Most of the modern upright pianos have three foot pedals also, but in most cases, the left and the middle foot pedals do not work quite the same as they do on grand pianos.
Una corda: On the upright piano, the left pedal is not truly considered to be a una corda pedal, because it does not shift the entire keyboard sideways to the right when depressed. In upright pianos, when the pedal is pushed down with the left foot, the hammers move closer to the strings, so that there is less distance for the hammers to swing. Therefore, instead of hitting fewer strings, each piano hammer strikes either all three or two strings assigned to each note with less force. The effect is a more quiet sound being heard instead of a softer sounding tone.
Sostenuto: Even if a piano has a middle pedal, true sostenuto function is quite rare to find on an upright piano. They can, however, be found on your higher guality and more expensive upright pianos.
Damper: The Damper pedal works the same way both on your upright and grand pianos, allowing the strings to vibrate, thus producing a sustained sound even after a note being played on the piano has been released.
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.
Piano Forums at Piano World
Join the World Famous Piano Forums at Piano World (it's FREE)