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                Violin and saxophone not included
                of a Piano
How the inside of a piano really works!


You play a note. You get a sound. Simple, right?

Not quite.

The piano was invented over 300 years ago, and while many inventions are improved upon over time, the piano managed to do something that hasn't been equaled by a keyboard instrument before or since. It is capable of responding to almost limitless varieties of human touch, producing sounds ranging in volume from thunder to a whisper and as many shades of sound as a gifted painter could produce on a canvas. Neither the instruments that preceded it (organ, harpsichord, clavichord, etc.) nor the modern day electronic keyboard which has replaced it in some places respond to the subtle imaginations of the player like the piano. It is not, however, such a simple matter to bring such a device into being.

When you depress a piano key, several things happen.

For starters, each key is actually about two feet long, most of which is hidden in the interior of the piano. While the front of the key is being pressed downward, the back of the key "lever" is ascending. But far from being like a see-saw, the rear of the key lever instead activates a spring that tosses the hammer at the string independently from the key itself. This is important. If the two parts weren't independent, the string wouldn't be able to vibrate freely when struck.

Try pushing a key down slowly. At about 2/3 of the way down you should feel a "bump" when the hammer is suddenly released at the string. If you depressed the key slowly enough you won't hear a sound because the hammer didn't have enough force to reach the string and cause it to vibrate. But the hammer was still tossed at the string, even if it didn't have enough energy to actually get there.

Here keys have just been struck. After striking the strings, the hammers have fallen about halfway down to their original position, poised to re-strike the string if the player retakes the key. They won't fall all the way down until the player releases the key entirely. This allows for quick repetition of notes since the hammers only have to travel half the distance in case of a key being re-struck. The dampers are still raised, allowing the string to keep vibrating until the player lets go of the key.
Piano hammers have to be able to do three things. Obviously, when the key is depressed, they need to make contact with the string so that the note sounds. But if that were all that were necessary, a simple see-saw contraption would do nicely. It isn't.

One of the piano's ancestors, the clavichord, had such a simple action. The problem is that in order to allow the string to keep vibrating the hammer must "let go" of the string. If it remains in contact, the sound that it created will be squelched. So in addition to hitting the strings, the hammer must fall back down and let the string it struck go on vibrating unhindered.

On the other hand, you can't have a hammer just bouncing around. If you struck a note with a lot of energy, it might come back up and strike the string a second time for each note you played. Two-for-one deals are not always desirable, which is why behind the hammers are felt "back-checks" to catch the hammer once it has fallen back off the string (the light brown items below).

The hammers are made of felt. Like many of the piano's parts, a number of materials were tried out during the 150 years between its first appearance (around 1700) and the last real innovations (1840s). Eventually, the hammers get hard and brittle and need to be shaved or they will break strings.


Dampers are cushions of felt which rest lightly on the strings for nearly the length of the piano (except the highest notes, which are considered too weak to need them).  If you try to pluck a string while the dampers are at rest,  you'll hear that the sound doesn't last very long. The string is being stopped from vibrating and is not going to make much sound. When you depress a key, the back end of the key lever is raised; besides tossing the hammer at the string the key is also connected (in a much simpler manner) to a rod connected to the damper and thus raises the damper off the string, allowing the string to vibrate on its own for as long as the key is held down.

With the keys and hammers taken out of the piano, you can see the thin metal rods that raise the dampers off the strings rising up from where the back of the key-lever would push them upward to the dampers above the strings, which of course you can't see from this angle (but trust me, they're up there somewhere).


Another way to raise the dampers is to depress the sustaining pedal. That would be the one on the right, regardless of whether your piano has three or two pedals. This foot-operated lever, sometimes mistaken for a gas pedal (and used similarly) was once operated with the knee (in Mozart's time). When you depress the pedal, all the dampers are raised at once throughout the piano. This allows every note you play to continue to sound for as long as the strings will vibrate or until you release the gas--er, sustaining pedal.

Two more pedals adorn most grand pianos. The one on the left is often referred to as the "soft" pedal. Its technical name is una corda, or one string, since, when deployed, it causes the entire action to shift slightly so that the hammers in the upper part of the piano, where there are three strings to a note, only strike one string. The effect of this is to make the piano softer, but it also changes the sound rather significantly. For this reason, many concert pianists maintain that using it in soft passages is really cheating. But as Leon Fleischer puts it, "There are many people who believe soft passages should be played without the use of the una corda pedal, and I go to them for confession every Sunday!"

The middle pedal, where one exists, is called the sostenuto pedal. It is a rather strange device which causes the dampers which are already off the strings to stay that way when you let go of the keys. In order to get it to work, you must first play a chord, and while you are holding it down, depress the pedal. Now those notes, and only those notes, will be sustained just like they would be if you had used the sustaining pedal. But any notes you play after the pedal is down will not be sustained. This pedal requires a good sense of timing, and, since most of our great composers didn't have one on their pianos, very little music actually makes use of that pedal, though I've occasionally found it useful for certain effects. All in all, however, it is the closest thing to  the piano's appendix. If your sostenuto pedal becomes inflamed, I highly recommend taking it out!

The green cushions below the keys are designed to give the keys something soft to land on when struck from above. They are just one of an amazing number of parts which should all be uniform throughout the piano's range. In this case the idea is to make each key travel the same distance to the bottom with each stroke so the player feels a consistency in the effort required to depress each key. I remember spending several hours in a piano maintenance workshop putting additional little paper donuts on top of the worn-out bushings so that the key depth would be equal. Let me add that there are also an insane number of screws throughout a piano's action that need to be adjusted as well! (This kind of operation is called "regulating" and is thankfully not done to a piano very often)


Pins and Pin block

Near the front of the piano, the strings are fastened to tuning pins which can be rotated to increase or decrease tension on the strings, thus raising or lowering their pitch.

Under the metal covering you see here is a dense, wooden block into which the pins are tightly driven. But not so tightly that a guy with a tuning hammer (looks a lot like a socket wrench) can't adjust the pin's position. A slight twist clockwise is enough to raise the pitch of the string. But it must be done carefully so the pin will stay in that position and not settle back into its old habit when the tuner leaves!

Hitch Pins

At the other end, the strings are looped around "hitch pins" or end pins.  Then the string is sent back to the next tuning pin at the front of the piano. What appears to be two different strings is actually two halves of the same string. These two halves may be used for different notes. The string is wrapped around the hitch pin tightly enough that this is possible. Adjusting one half of the string does not affect the other half.


The bass strings are thick and coiled for more power. At the low end of the piano one string serves for each note and is not wrapped around hitch pins. After the first octave, a thinner string is deployed and two of them are used for each note. For most of the piano, however, the strings are thin and are deployed in sets of three to a note (that is, three string halves)

I know a tuner who broke a bass string once while tuning. The long end shot out of the piano and smashed a plate glass window! Not only do these things growl, they can be dangerous when aroused!

The agraffes are metal bridges with little holes for the piano strings to slide through. Their purpose is to guide the strings precisely into position above the hammers. If they are off by even a little, you will not hear the note you thought you played. Worse, you could hear parts of two of them. 
On the other end, graphite bridges with tiny pins on each end guide the strings into position for their ride around the hitch pins. Between the agraffes and the graphite bridges is what is known as the string's "speaking length". The strings do not vibrate beyond those points. Sometimes felt is inserted to the strings on these ends to give additional help in muting the strings. If they vibrated along their entire length, the tuning pins and hitch pins would share in the vibration. It is not particularly beneficial to have that many metal parts vibrating unnecessarily!



This is the entire "action" of the piano removed. You can see how the hammers have their own rail above the key levers. When the key is depressed, the back of the key lever strikes the back of the hammer apparatus, and the hammer is tossed at the string at the same rate of speed as the key was pushed down to begin with. This allowed the instrument to be played loudly or softly depending on the player's actions. It was the first keyboard instrument that allowed this, and was thus named the Pianoforte, which is a collision of the Italian words for soft (piano) and loud (forte). 


 If anybody has any ideas about what those craters are for, let me know.


much thanks to Rosanne Ruffo for allowing me to take apart her piano and for her excellent photography.

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