How A Piano Works
A piano consists of numerous parts that each perform a specific function. When combined they produce the beautiful sound we hear eminating from the instrument. Below is a series of descriptions describing the major parts of a piano and how they come together to make a piano work. Here are some diagrams to help you visually understand each component being described.
1. The Strings - The strings, numbering over 200, are long metals wires that are stretched taughtly across the piano's plate. The tension and length of each string determines its pitch. A string that is longer and under less tension produces a lower pitch than one that is shorter and tighter. One end of a piano string is attached to a tuning pin. The string then passes along the plate and either loops around or is tied to a hitch at the other end of the plate. If the string is looped it passes back across the plate and up to another tuning pin, where it is attached and ends.
2. The Plate - The piano plate is a large cast iron object which is designed to overcome the enormous amount of string tension that the piano is burdened with. If a piano did not have a plate then the wooden frame of the piano would not be able to withstand the thousands of pounds of pressure that are exerted from the strings; instead the instrument would buckle or bow considerably. Imagine an archer's bow: a straight piece of wood is caused to bow due to the string's tension placed upon it. The same would happen to a piano without a plate.
3. The Pinblock - The pinblock is a robust block of wood that is made by laminating pieces of hardwood together in opposing directions. This laminating and crossing of wood grain direction gives it great stability, which is critical and the determing factor in maintaining tuning stability. The pinblock has holes drilled into to receive the tuning pins. These tuning pins have very slight threads, which allow them to be screwed into the pinblock. If the tuning pins cannot remain firmly seated in the pinblock then the string tension will loosen, causing the piano to go out of tune.
4. The Soundboard - If you consult the diagrams you will see that we have a plate sitting atop of a pinblock and with strings running across it. The strings are attached on one end to the tuning pins and on the other end to the hitches on the plate. Let's imagine for the moment that we attached the keyboard and action, allowing us to have the hammers strike the strings. the sound produced would be very minimal and not exactly pleasing to the ear. This is where the soundboard comes in. It could be called the heart and soul of the piano because it is what amplifies and gives the volumes of sound that we hear from the piano. It is basically a large thin wooden membrane usually made of spruce. The soundboard sits inside the piano, with it's edges attached by glue to the piano's structual frame. This leaves the vast majority of the soundboard's area free to vibrate. Two wooden strips are attached to the front (string) side of the soundboard. One is the bass bridge and the other is the treble bridge. Theey correspond to the low and high strings of the piano, which cross over and bear down on them. Now, with the plate and its taught strings sitting atop the soundboard the strings are able to bear down on the bridges that protrude through the cutouts in the plate. Thusly, all vibrations that are produced from the string being struck by a hammer are now transferred to the bridge and onto the soundboard. The soundboard now vibrates and excites the air around it - producing the sound we hear. The larger the soundboard, the larger the magnitude or volume of the sound we hear. So, stated simply - the soundboard amplifies the low volume string vibrations into a much larger sound.
5. The Action - This is, without a doubt, the piano's most complicated mechanism. The piano action translates the players motions on the keyboard into the striking of a piano string. Otherwise the player would need to pluck each string with their hands - but that would be a harp, not a piano. The piano action consists of all mechanical parts between the keys and the hammers, which strike a string. For each key there are (depending on who you ask) 5-100 separate parts, each with a specific function. It must be noted that the grand and upright piano actions differ in the operation, but both perform the same function as stated above. The best way to learn how a piano action works is to see it in real time. Here are some informative videos to help you understand better.
6. The Frame - The piano frame provides the piano with just that - a structural frame to hold all in things in place. Virtually every major part of a piano is attached and secured in some way to the piano frame. With an upright piano this frame is often referred to as the back becuase it is in the back and against the wall. It consists of a square wooden frame made up of thick peices of wood. This square is further supported by crossbracing and supports to enable help ensure the piano's structural inegrity. On a grand piano the frame is underneath the plate and soundboard and is covered up by the rim, which bands or wraps around the entire piano.
7. The Cabinet - The cabinet of a piano serves no structural purpose and is mainly for aesthetic purposes. All of the pretty woodwork that you see on a piano is primarily part of the cabinet and serves no instrumental purpose. However, the rim of the grand piano does serve an acoustic purpose in addition to being considered part of the piano's cabinet. Although there is room for debate on this issue, the grand piano rim is believed to compliment the soundboard's vibrations and therefore affect the acoustic properties of the piano. But, much of this is dependent on the construction techniques and type of wood used for the rim.