how does a piano work ?
HOW DO THE PEDALS WORK ?
The internal mechanism is called the "action", and for each note played (for 2/3 of the piano), there are 4 main moving parts.
1. Piano key 2. Undercarriage 3. Hammer 4. Damper
For the remaining third (1/3) top treble notes, there are no dampers, so parts 1, 2 and 3 apply.
To view an upright piano action working, you must remove the front panel and fallboard (lid that covers the keys).
There are approximately 6,000 individual parts inside a piano action.
To ensure that all parts move smoothly and "mechanically" sound as quiet as possible (except for the string), all parts that contact each other are protected and covered with various different materials. Some parts that require greater friction have thicker, more robust material; the materials used are leather, baize, cloth and felt. Some materials are softer than others so that they can rebound and return to rest quietly, without any clicking or tapping noises. There are also special parts to hold the action together, to prevent it from collapsing or dislocating itself when the action is removed. For keyboard materials, fine adjustments must be made to the thickness of materials, and so paper / tissue paper and card washers are used as spacers underneath various baize or cloth washers.
There is never any wood to wood or wood to metal contact with parts, they are always sandwiched with materials.
A piano action consists of about 90% wooden parts - usually hard wood like maple, mahogany, hickory, walnut - these woods ensure a longer life for the piano, and less likely to break or warp.
If you press a note slowly, watch what happens !
Click on any image to enlarge.
THE UPRIGHT PIANO ACTION - UNDER DAMPED (Modern)
Stage 1
(1) Key pressed down
(2) Raises back of key / sticker capstan (stickers are the long pieces of wood- optional)
(3) Raises the undercarriage
(4) Jack pushes on the hammer butt forward
(5) Hammer starts to move towards string
About 50% of this movement 1 - 5 is carried out first, before the damper moves.
(1) Key pressed down
(2) Raises back of key / sticker capstan (stickers are the long pieces of wood- optional)
(3) Raises the undercarriage
(4) Jack pushes on the hammer butt forward
(5) Hammer starts to move towards string
About 50% of this movement 1 - 5 is carried out first, before the damper moves.
Stage 2
After 50% movement of the action >>
(6) Damper spoon connects with the lower damper lever.
(7) Damper head and felt begins to move away from string
Some older pianos have the dampers over the top of the hammers - over-damped.
These work in a similar way, but operated by lift wires at the front of the undercarriage (3)
All dampers should be activated AFTER the rest of the action starts.
After 50% movement of the action >>
(6) Damper spoon connects with the lower damper lever.
(7) Damper head and felt begins to move away from string
Some older pianos have the dampers over the top of the hammers - over-damped.
These work in a similar way, but operated by lift wires at the front of the undercarriage (3)
All dampers should be activated AFTER the rest of the action starts.
Stage 3
(8) As the jack rises pushing the hammer forward, the jack toe (immediately left of 8) bumps into the set-off button above it, creating "escapement". This allows the hammer to trip just before it
reaches the string. This movement prevents the hammer from blocking against the string and also allows the jack to free itself away from the hammer. .
All the other parts are now fully engaged and have reached their optimum distance.
Did you know?
If a key is pressed gently, the jack will produce less force, giving a softer tone (p = piano)
If the key is pressed hard, the jack will produce more force, giving a louder tone (f = forte)
Hence the term "piano-forte" (meaning soft & loud) is taken from the name of this instrument.
For short, we call it a piano, but it's full name is pianoforte.
When the jack pushes the hammer towards the string, the hammer makes the sound on the string, not the jack.
(8) As the jack rises pushing the hammer forward, the jack toe (immediately left of 8) bumps into the set-off button above it, creating "escapement". This allows the hammer to trip just before it
reaches the string. This movement prevents the hammer from blocking against the string and also allows the jack to free itself away from the hammer. .
All the other parts are now fully engaged and have reached their optimum distance.
Did you know?
If a key is pressed gently, the jack will produce less force, giving a softer tone (p = piano)
If the key is pressed hard, the jack will produce more force, giving a louder tone (f = forte)
Hence the term "piano-forte" (meaning soft & loud) is taken from the name of this instrument.
For short, we call it a piano, but it's full name is pianoforte.
When the jack pushes the hammer towards the string, the hammer makes the sound on the string, not the jack.
Stage 4
SUSTAINING A NOTE
When a note is held down and sustained, the hammer hits the string and rebounds (5).
The damper (7) remains off the string to allow the string to sound.
During the rebound (within a split second), the back of the hammer catches the back check at (9)
This prevents the hammer from rebounding again (known as bubbling).
One clean "hit" of the hammer, then it is caught at (9) like catching a ball being thrown.
PLAYING STACCATO
If a note is played "staccato" (short & detached), parts 9 are not engaged.
When the piano key is released, the damper spring moves the damper back to the string (to mute the sound), the jack spring moves the jack back under the hammer butt, then the hammer and undercarriage return to their positions by gravity as in stage 1. If the hammers are spring assisted (butt springs), this will give better repetition of the same note (e.g. trill) from stage 2 to 4.
When the hammer returns to rest, it falls back onto the hammer rest rail (not illustrated).
The cycle now starts all over again!
For the top two octaves or so (top third), there are no dampers for these strings. This is because the strings are shorter and their sustaining power is much less than the lower notes. However, an overstrung piano often helps to sustain these notes on their own (sympathetic vibration) as the strings cross over. The sound quickly dies away for these top treble notes, so dampers are not needed.
This is easier to view on a grand piano by simply opening the top lid.
For an 85 or 88 note piano (7 or 7 1/4 octaves), there are usually about 65 dampers.
SUSTAINING A NOTE
When a note is held down and sustained, the hammer hits the string and rebounds (5).
The damper (7) remains off the string to allow the string to sound.
During the rebound (within a split second), the back of the hammer catches the back check at (9)
This prevents the hammer from rebounding again (known as bubbling).
One clean "hit" of the hammer, then it is caught at (9) like catching a ball being thrown.
PLAYING STACCATO
If a note is played "staccato" (short & detached), parts 9 are not engaged.
When the piano key is released, the damper spring moves the damper back to the string (to mute the sound), the jack spring moves the jack back under the hammer butt, then the hammer and undercarriage return to their positions by gravity as in stage 1. If the hammers are spring assisted (butt springs), this will give better repetition of the same note (e.g. trill) from stage 2 to 4.
When the hammer returns to rest, it falls back onto the hammer rest rail (not illustrated).
The cycle now starts all over again!
For the top two octaves or so (top third), there are no dampers for these strings. This is because the strings are shorter and their sustaining power is much less than the lower notes. However, an overstrung piano often helps to sustain these notes on their own (sympathetic vibration) as the strings cross over. The sound quickly dies away for these top treble notes, so dampers are not needed.
This is easier to view on a grand piano by simply opening the top lid.
For an 85 or 88 note piano (7 or 7 1/4 octaves), there are usually about 65 dampers.
HOW DO THE PEDALS WORK ? (Upright piano)
On an upright and grand piano, the RIGHT pedal is always the sustain pedal (mechanism always veers off to the left).
The left and middle pedals vary depending on the piano.
The diagrams have been simplified, removing some of the components, but show the basic way how each pedal works.
RIGHT PEDAL
This pedal allows all the strings to sustain together, and removes all the dampers from the strings in one go.
Correctly called the sustain pedal, it is sometimes nicknamed the "loud" pedal as it tends to make the piano sound louder.
Pedal mechanisms are quite simple on most pianos, and rely on two pedal levers; A. Horizontal rocker lever. B. Vertical lift rod lever
The vertical rod is then connected at the top to an external crank lever on the mechanism to activate the dampers.
On an upright and grand piano, the RIGHT pedal is always the sustain pedal (mechanism always veers off to the left).
The left and middle pedals vary depending on the piano.
The diagrams have been simplified, removing some of the components, but show the basic way how each pedal works.
RIGHT PEDAL
This pedal allows all the strings to sustain together, and removes all the dampers from the strings in one go.
Correctly called the sustain pedal, it is sometimes nicknamed the "loud" pedal as it tends to make the piano sound louder.
Pedal mechanisms are quite simple on most pianos, and rely on two pedal levers; A. Horizontal rocker lever. B. Vertical lift rod lever
The vertical rod is then connected at the top to an external crank lever on the mechanism to activate the dampers.
1. Pedal depressed
2. At A, rocker goes down at pedal end, goes up at other end, like a see-saw
Hinged in the middle with a large pin (red) and spring underneath.
3. At B, lift rod rises towards mechanism
4. Lift rod pushes up on damper crank lever C to activate dampers
The damper crank lever is at the back of the mechanism, always on the left.
The lift rod B is usually guided with a bushed block of wood or another lever.
A + B levers are either wood or aluminium. C is always steel or cast iron.
There are some upright pianos that have a torsion bar & steel wire spring instead of A. As the bar revolves anti-clockwise, this connects to B rod in the same way as above.
2. At A, rocker goes down at pedal end, goes up at other end, like a see-saw
Hinged in the middle with a large pin (red) and spring underneath.
3. At B, lift rod rises towards mechanism
4. Lift rod pushes up on damper crank lever C to activate dampers
The damper crank lever is at the back of the mechanism, always on the left.
The lift rod B is usually guided with a bushed block of wood or another lever.
A + B levers are either wood or aluminium. C is always steel or cast iron.
There are some upright pianos that have a torsion bar & steel wire spring instead of A. As the bar revolves anti-clockwise, this connects to B rod in the same way as above.
LEFT PEDAL
Often referred to as the "soft" pedal, on most upright pianos, this pedal brings the hammers closer to the strings (as shown).
On old pianos (pre 1920), the soft pedal relied on a celeste rail & felt to mute the sound - similar to a modern upright middle pedal.
At A + B, rocker and lift rod work the same way as for the right pedal.
These levers are located in front of the sustain pedal levers.
At C, there should be a small gap between B rod and C crank lever.
When the pedal is depressed, the crank lever C pushes the hammer rest rail forwards, so all hammers are closer to the strings. There is always some "play" here so that the hammers are not too close.
This helps the pianist to play the notes softer.
On most modern upright pianos with a soft-fallboard mechanism (e.g. Kawai), B rod is removed to gain easier access to the screws,
prior to tuning. Some pianos have this mechanism on the right side (e.g. Bechstein Model 10) and instead of a felt pad, a leather tongue and groove is used. At the top of B, (green felt), this felt is sometimes replaced for leather, or a rubber grommet and pin.
MIDDLE PEDAL - OFF
On any upright piano fitted with a middle pedal, this is known as a "practise" pedal, and produces a greater muted sound.
This pedal must not be confused for a grand piano middle pedal - this has a different function.
A + B levers are now replaced with one long continuous steel wire inside a plastic sleeve, like a gear change lever on a bike.
MIDDLE PRACTISE PEDAL MECHANISM
At rest, showing the suspended celeste rail at the top. This rail has graded thicknesses of felt from thick to fine. Thick felt for the bass / thin for treble.
In this "off" position, the rail (not wire) must be removed prior to tuning.
This mechanism can also be fitted as an optional extra kit to most upright pianos with an under-damped mechanism, but instead of a middle pedal, a lever is fitted instead underneath the keyboard. (See below)
At rest, showing the suspended celeste rail at the top. This rail has graded thicknesses of felt from thick to fine. Thick felt for the bass / thin for treble.
In this "off" position, the rail (not wire) must be removed prior to tuning.
This mechanism can also be fitted as an optional extra kit to most upright pianos with an under-damped mechanism, but instead of a middle pedal, a lever is fitted instead underneath the keyboard. (See below)
MIDDLE PEDAL - ON
When the middle pedal is depressed, it then slides to the left and locks into place - for practising purposes. Note its position on the diagram.
The celeste/ felt rail now moved down covering the strings where the hammers are. (Far left) - A = string. B = Celeste/felt rail. C = Hammer.
The hammers now strike the strings "through" felt to create a muted sound; far greater than the left pedal.
CELESTE RAIL + FELT KIT (Optional)
Acting as an upright piano middle practise pedal, a kit is available as an optional extra.
For pianos with 2 pedals (soft & sustain), the kit fits neatly inside your piano and no need for a 3rd pedal.
A gear lever is fitted under the keyboard (completely out of sight) to operate the celeste rail & felt.
1. Rail comes in 2 halves / bolted together and adjusted for your piano width.
2. Cable wire may run at either end (opposite end to lift rods B)
3. Level of DIY skill : 7/10 - Medium (for a standard upright piano)
4. Kits comes with rail, felt, cable, lever and all screws/ washers & fixtures.
(The cable is factory fitted to the lever)
5. FREE FITTING by AA Piano Tuners - local - please ask.
NOTE: This kit cannot be fitted to an existing middle pedal, nor can it be fitted to an upright piano with an over-damped action (bird cage) or any grand piano.
For more information/ price, please contact Colin - 0791 485 4072
2. Cable wire may run at either end (opposite end to lift rods B)
3. Level of DIY skill : 7/10 - Medium (for a standard upright piano)
4. Kits comes with rail, felt, cable, lever and all screws/ washers & fixtures.
(The cable is factory fitted to the lever)
5. FREE FITTING by AA Piano Tuners - local - please ask.
NOTE: This kit cannot be fitted to an existing middle pedal, nor can it be fitted to an upright piano with an over-damped action (bird cage) or any grand piano.
For more information/ price, please contact Colin - 0791 485 4072
GRAND PIANO PEDALS
The pedals on a grand piano are connected to the levers by a separate mechanism - the pedal lyre.
The pedal lyre is designed to be removed (if needed) for a grand piano removal, and it is separated from the piano, leaving the levers in place under the piano - so whereas an upright pedal system is built-in, a grand pedal system is a separate unit.
The right sustain pedal lifts the dampers, like an upright piano, however the internal damper mechanism is separate to the rest of the action. The best way to describe this is to view and play a grand piano.
RIGHT SUSTAIN PEDAL - off position
The pedals on a grand piano are connected to the levers by a separate mechanism - the pedal lyre.
The pedal lyre is designed to be removed (if needed) for a grand piano removal, and it is separated from the piano, leaving the levers in place under the piano - so whereas an upright pedal system is built-in, a grand pedal system is a separate unit.
The right sustain pedal lifts the dampers, like an upright piano, however the internal damper mechanism is separate to the rest of the action. The best way to describe this is to view and play a grand piano.
RIGHT SUSTAIN PEDAL - off position
Showing basic layout of the sustain pedal workings
A = lyre lift rod (brass)
B = rocker lever (cast iron)
C = connecting lift rod to damper rail/ levers (usually a wooden dowel)
At C, a 10/11mm hole is drilled through the key bed and bushed
The damper levers are connected to the dampers by lift wires (not shown)
As an upright piano, grand dampers only needed for 2/3 of the strings
If the pedal lyre is required to be removed, lift rod A and lever B easily separate as B just rests on A.
RIGHT SUSTAIN PEDAL - on position
A: Pedal depressed, lifting brass rod passing through bushed cross member
B: Intermediate lever is operated, sometimes connected to another lever
C: Wooden dowel/ short bar lifting damper rail
The damper rail lifts all damper levers together.
Each damper lever has a long wire attached that passes through the strings.
Damper heads & felts are now raised above the strings
GRAND PIANO LEFT PEDAL - UNA CORDA
The left (soft) pedal mechanism is unique to grand pianos only (except for some pre 1900 German uprights).
This pedal actually changes the sound of the piano by sliding the hammers and keys to the right, so the hammers hit a smaller portion of the strings. For a treble tri-chord, the hammer hits two of the three strings (middle & right), leaving the left string not struck, but to vibrate against the other two strings - called "sympathetic vibration". Bass strings are struck by a smaller portion of a bi-chord and single string. In this case, the hammer briefly "brushes" the left side of each string, so mainly striking the right portion. This "unstruck" portion is what is referred to as "una corda" - meaning "one string". So the hammers do not strike only one string. This unique design allows the pianist to make fine adjustments to the tone, creating a somewhat "silvery" (thinner) sound.
On a piece of sheet music, "una corda" means to depress the left pedal; "tre corda" means to release the left pedal (3 strings) - although the release term is used loosely, as it doesn't apply to the bass strings as such.
A: Lyre lift rod resting on B lever
B: Canter lever that rocks to the right, resting against keyboard underside
Lever B requires a massive amount of leverage, so it is manufactured as one complete L shaped lever from cast iron. Also the keyboard rebate slot is encased in strong steel to support the weight and sliding action.
(not shown) - very strong leaf spring between RH action and inner cheek.
This assists the return of the action & keyboard.
Compare the positions of keyboard & mechanism off then on.
Lift rod A pushes against canter lever B
B lever lifts (a fraction) and slides mechanism & keyboard to the right
All keys slide as the lever pushes on the key frame, between keys & bed.
Dampers and strings do not move
As shown, hammers strike a smaller portion of the strings
For servicing purposes, it is very important to periodically keep the key bed top surface as clean as possible to allow the key frame and mechanism to slide smoothly under light friction. Any small pieces of grit or dirt may cause the action not to return or not return fully.
The return spring may need to be re-tensioned and a light dusting of French chalk used for the mechanism to work efficiently.
THE GRAND PIANO ACTION
A grand action works mainly using gravity for those parts that "fall" such as the hammer, undercarriage and damper, giving the action a more natural feel. Where a hammer and damper are in an almost vertical position on an upright action (moving back and forth), and relying on springs for their return journey, on a grand action, the damper and hammer drop by means of gravity (moving up and down) - so no springs are needed.
The grand action works in a similar fashion to the upright, requiring a key, undercarriage, jack, hammer and damper, but the grand action has an additional part up its sleeve that the upright doesn't have...... a repetition lever; this will be explained later.
The grand action has an independent damper system, which is separate to the main action, and is located deep in the bowels of the piano, behind the main action. When the main action and keyboard are pushed home into the key bed, then it connects to the damper system. The upright action has an all-in-one damper mechanism incorporated into the rest of the action.
How the grand action works..... (click to zoom)
Stage 1: Key starts to move down at the front (1); Capstan and undercarriage is raised at (2);
Also raising the jack (3), hammer roller/ shank and hammer head (4).
At this stage, the jack (3) passes through an open "window" on the repetition lever to connect with the hammer roller above it, so when the action is at rest, the hammer roller rests on the repetition lever, not the jack.
Stage 2: As the key rises further at the back (50%), it begins contact with the damper lever at (5).
Stage 3: The jack disengages from the hammer roller at (6) when the jack toe bumps into the set-off button at (X).
In slow motion, the hammer trips just before it reaches the string, the last bit of its journey is done by inertia.
At (7), the damper head & felt fully disengage from the string (before the hammer hits the string) to allow the string to vibrate.
[When we refer to "string", this will either be one, two or three strings depending on the pitch]
Stage 4: (Sustained note) >> With the piano key pressed down and held firmly (8), in a flash, the hammer (9) simultaneously strikes and rebounds from the string using upward force from the jack, then inertia, then gravity and its weight takes over. The force of gravity combined with the weight of the hammer depresses the repetition lever (below the roller) enough to bypass the jack at (10), and at the same time, the back check catches and holds the hammer in "check" at (11) - to prevent the hammer from rebounding back to the string. The repetition lever spring is tensioned in such a way to prevent the lever from collapsing too far, and remains in this "cocked" position, ready for the bit of magic to follow !...... the next part is what separates grand pianos from upright pianos.
Stage 5: (Quick repetition) >> For repeating the same note quickly, or performing a rapid trill (quick alternation of two notes played in succession, e.g. C + D), when the front of the key rises a little at (12), the back check releases the hammer at (13).
This then allows the repetition lever (14) to lift the hammer until the jack returns under the roller.
The action is ready for another cycle of quick repetition, even though the key hasn't returned all the way to its rest position.
This is why you will see a Concert Pianist perform on a modern grand piano, and not an upright piano.
On an upright piano, the key has to almost fully return to rest to allow the jack to reset itself, resulting in weaker repetition, because upright pianos do not have a repetition lever - only grand pianos have this unique part.
Stage 5 zoom / Quick repetition >>
Let's have a closer look at the repetition lever in relation to the jack and roller.
The repetition lever is at about a 45 degree angle to the undercarriage below it, and hammer above it. This is the part the roller rests on.
Looking at the diagram to the right (below), for clarity the rep lever is horizontal - just to show it off better !
At rest and during repetition stages, the tip of the jack must always be below the level of the repetition lever, by exactly 1mm, so that the jack does not touch the roller, but literally "glance" past it...... this is critical. .
During the servicing of a grand piano action, this tiny gap must be checked and adjusted if necessary.
No gap = jack may not return under roller/ not return quickly enough / intermittent repetition problems.
Larger than 1mm gap = may cause the note not to work/ feeling "notchy" under the piano key / incorrect touch.
1mm gap = action will play beautifully and if needed, at lightning speeds.
At rest, the jack must also be perfectly aligned under the roller - too far to the right or left, and the note will not work properly.
The centre inner core of the roller must line up with the jack line groove on the repetition lever - get your technician to check this out.
General wear and tear of regulating button felts cause misalignment of these parts due to normal compression.
Let's have a closer look at the repetition lever in relation to the jack and roller.
The repetition lever is at about a 45 degree angle to the undercarriage below it, and hammer above it. This is the part the roller rests on.
Looking at the diagram to the right (below), for clarity the rep lever is horizontal - just to show it off better !
At rest and during repetition stages, the tip of the jack must always be below the level of the repetition lever, by exactly 1mm, so that the jack does not touch the roller, but literally "glance" past it...... this is critical. .
During the servicing of a grand piano action, this tiny gap must be checked and adjusted if necessary.
No gap = jack may not return under roller/ not return quickly enough / intermittent repetition problems.
Larger than 1mm gap = may cause the note not to work/ feeling "notchy" under the piano key / incorrect touch.
1mm gap = action will play beautifully and if needed, at lightning speeds.
At rest, the jack must also be perfectly aligned under the roller - too far to the right or left, and the note will not work properly.
The centre inner core of the roller must line up with the jack line groove on the repetition lever - get your technician to check this out.
General wear and tear of regulating button felts cause misalignment of these parts due to normal compression.
Parts omitted from diagrams: upright damper/ jack slap rails, grand hammer rest rail, sostenuto mechanism, (pedal diagrams) - grand piano legs and miscellaneous parts.
These diagrams and descriptions serve as a guide only; certain procedures may have been omitted for clarity reasons, and the various naming of parts has been simplified. These do not serve as instruction manuals. Celeste rail kits can only be fitted to certain upright pianos (some mentioned above), so please contact your piano tuner for more information.
All this information is subject to change, depending on the style and age of a piano.
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These diagrams and descriptions serve as a guide only; certain procedures may have been omitted for clarity reasons, and the various naming of parts has been simplified. These do not serve as instruction manuals. Celeste rail kits can only be fitted to certain upright pianos (some mentioned above), so please contact your piano tuner for more information.
All this information is subject to change, depending on the style and age of a piano.
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