Piano Glossary

A short compilation of basic & simple terminology and definitions for parts commonly used in the rebuilding process.

Piano ActionAction:
The playing mechanism(s) of the piano.



AgraffeAgraffe: A guide (usually brass) in which unison strings pass through to make a termination point at the end of the string toward the front of the piano. Agraffes are screwed into the cast iron plate, (or harp) and acts as a physical anchor for and also regulate the height of the string unison.


BackcheckBackcheck: A suede, leather or felt covered catcher which is fastened to the end of the piano key via a wire post. The backcheck “catches” and holds the piano hammer just after it has rebounded from striking the string and while the action below the hammer is preparing for another repetition of the note.


piano belly


Belly: The piano soundboard area. Included in the generic term for the belly “area” may be the soundboard, bridges, belly rail, dampers, plate (harp) tuning pins and pinblock.



 BridgeBridge: Treble and Bass: Long shaped and carved hardwood rails usually maple or other hardwood, which span across the soundboard and guide strings to transfer vibration from strings to the bearing surfaces of the bridge to the soundboard. Bridges are sometimes capped, are notched and are pinned for unison groupings of strings.

Bridge Pins:
Steel, chrome, nickel, brass or copper plated pins seated into the bridge (either treble or bass) to exert side bearing to strings upon the bridges and align strings for proper spacing at the bridges.

CapstanCapstan: A threaded brass nut with polished top cap that is inserted into the top of the back end of the piano key. The whippen is raised via the piano key when depressed in order to begin the process of parts rotation and deliver the piano hammer to the string.

FlangeFlange: a part which is fastened to and enables other major components to travel. Flanges found within the action such as the whippen flange or hammer flange allow those major components to travel in an arc. Flanges have tiny pivot holes drilled through them and are attached to their respective major component via a center pin.


piano hammerHammer: A felted mallet which is driven to the strings by the piano action to participate in producing piano sound. Piano hammers have a spring like action due to two present forces: tension and compression. Highly compressed felt is formed around a wood core under tremendous pressure to make piano hammers.

HammershankHammer shank & flange:
A hardwood dowel which connects the hammer to the hammer flange. Also shown is the knuckle which is attached to the underside of the hammershank.


KeyKey: A dual lever arm which pivots at the balance rail. Piano keys are made of soft wood (conifer) varieties including sugar pine, basswood and sometimes spruce. The back end of the piano key raises the whippen via the capstan which consequently raises the hammer toward the string. The piano key is in itself a complex mechanism which includes weights for control of touch weight, the key- top, button, capstan, backcheck and two mortises for felt bushings.

Keytop, SyntheticKeytop: A key covering of ivory in the case of older pianos, or synthetic plastic in more modern pianos which covers only the top and front surfaces as a veneer to the key. Shown in this picture is a synthetic covering.

Key ButtonKey Button: A felt bushed wooden plate installed at the top of the piano key to add strength, and help guide the key during travel.



Key Bushing(s): Felt inserts at the key front and balance mortises which help to align and guide key travel during play. Key bushings are carefully regulated for minimum resistance or friction during play.

DamperDamper: Soft block or triangular shaped felts which are timed to stop the vibration of the piano strings at a carefully calculated point. Therefore, dampers silence vibrating strings when they are rested upon them. This either occurs at the release of the piano key or when the right or “sustain” pedal is released and no notes are held by contact with the piano keys.


IvoriesIvory (ies): Traditional (older) key coverings made from elephant and other mammal tusk material.


Keybed: The structure upon which the keyframe, keys and action rest inside the piano.

A wooden frame consisting of slats and rails which holds the keys and action. The keyframe has two rails with complete sets of keypins for guiding key travel, glides which are incorporated into the underside of the keyframe for bedding purposes and to reduce friction at the shift position of the una-corde pedal. Three rails which are the front, balance and back rails are all felted for different function of key travel and rest.

KeypinKeypin:  A nickel plated steel pin found at the front and center rails of the keyframe for key alignment and travel purposes.




Natural(s): White keys or keys that are not “sharps”.

PedalsPedals & Pedal Lyre:  Levers which the feet control to either sustain notes being played (right or sustain pedal), soften tone from piano by shifting the action to change hammer contact with strings (the left or una-corde pedal, or to sustain individual notes being played (the middle or sostenuto pedal).

Pinblock MaterialPinBlock: Sometimes also called the “wrest-plank”, the pinblock is a large thick multi layered block of hard wood (often hard rock maple) used to anchor tuning pins. The block is fastened to a shelf at either end of the piano’s inner rim with dowels and screws. The purpose of the pin block is to provide resistance to tuning pin torque which is required to keep individual strings and notes at “pitch”.

A term used to describe the physical adjustments necessary to allow the complex mechanisms of the piano action to cycle properly and therefore to optimize touch, response and tone. Regulating a piano requires many steps which include:

  • Keyframe bedding to keybed
  • Necessary repairs to the action
  • Friction reduction
  • Key rebushing
  • Key height, square and leveling
  • Parts alignment
  • Repetition spring adjustment
  • Jack and repetition lever alignments
  • Let off and drop regulations
  • Jack tail and drop screw to contact points timing and synch
  • Backcheck alignment and adjustments
  • Damper timing and regulations
  • Voicing of piano hammers

Piano TuningPiano Tuning:
Piano Tuning is a process and procedure which ultimately alters the pitch and timbre of our instrument. We use tuning as a means to positively change the intonation of the piano to best suit our standard of equal temperament and compliment the diatonic scale.

Because it has been determined that the equal tempered scale is the most acceptable configuration for our musical traditions, we have long designed our pianos to work best with this standard.

Piano tuning is therefore the physical manipulation and movement of the approximately 209 tuning pins which will in turn alter the tension of the wire which is attached to each tuning pin, in order to alter pitch, either higher (sharp) or lower (flat). Each note is “set” at a place which contributes to an overall formula for the distribution of frequencies and beat rates that we find most pleasing to our ear.

SharpSharp(s): Another term for black keys.


Shim (Soundboard)Soundboard:
 is an arched wood panel covering the entire area under or behind the piano strings within the inner rim of the piano which transmits the vibrations of the strings to the air. This is done via treble and bass bridges. High quality piano soundboards are made of solid spruce panels similar to the width of the hand and joined together to form one large panel. Spruce varieties transmit sound well and are suitable for this difficult and critical task due to large open cell structures and a very high strength to weight ratio.

Tuning PinTuning Pin: Threaded steel “peg” around which the piano wire around which every string is wound. Commonly approximately 2 ½ inches long, each tuning pin is seated by pounding approximately 1 ½ “ into a laminated wooden wrest-plank or pin block made of maple in order to keep strings in tune.

WhippenWippen (Repetition):
is a central combination component of the piano action. Also known as the “repetition”, wippens or repetitions facilitate parts rotation(s) which occur between the piano key and the piano hammer. Via a complex series of interactions and motions each note is capable of playing, repeating and becoming ready to play again in large part due to the individual components encompassed within, and the overall function of the whippen. The whippen is housed above and on top of the piano key and below the piano hammer.

Base StringWire, Bass String(s): Heavy gauge strings which are found in the bass and sometimes tenor sections of the scale, bass strings are steel core with copper windings of differing diameters depending on their position in the scale.

Piano TrebleWire, Piano (Treble):
Steel wire of differing diameters found in sections other than the bass of the piano scale.