Many teachers encourage "use of the whole body for playing the piano" (see Whiteside). What does that mean? Are there special body motions that are required for technique? Not really; technique is in the hands and relaxation. However, because the hands are connected to and supported by the body, you can't just sit in one position and hope to play. When playing the upper registers, the body should follow the hands and you might even extend one leg in the opposite direction in order to balance the body, if it is not needed for the pedals. Also, even the smallest motion of any finger requires the activation of a series of muscles that lead all the way to at least the center of the body (near the sternum), if not all the way to the legs and other members that support the body. Relaxation is as important in the body as in the hands and fingers, because of the shear size of the muscles involved. Therefore, although most of the required body motions can be understood from simple common sense, and do not seem to be that important, they are nonetheless absolutely essential to piano playing. So let's discuss these motions, some of which may not be totally obvious. The most important aspect is relaxation. It is the same type of relaxation that you need in the hands and arms -- use of only those muscles required for playing, and only for the brief instants during which they are needed. Relaxation also means free breathing; if your throat is dry after a hard practice, you are not swallowing properly, a sure sign of tenseness. Relaxation is intimately related to independence of every part of the body. The first thing you must do, before considering any useful body motions, is to make sure that the hands and fingers are totally decoupled from the body. If they are not decoupled, the rhythm will go awry, and you can make all sorts of unexpected mistakes. If, in addition, you don't realize that the body and hands are coupled, you will wonder why you are making so many strange mistakes for which you cannot find the cause. This decoupling is especially important in HT play, because the coupling will interfere with the independence of the two hands. Coupling is one of the causes of mistakes: for example, a motion in one hand creates an involuntary motion in the other through the body. This does not mean that you can ignore body decoupling during HS practice; on the contrary, the decoupling should be consciously practiced during HS work. Note that decoupling is a simple concept and easy to execute once you learn it but, physically, it is a complex process. Any motion in one hand necessarily produces an equal and opposite reaction in the body, which is automatically transmitted to the other hand. Thus decoupling requires active effort; it is not just a passive relaxation. Fortunately, our brains are sufficiently sophisticated so that we can easily grasp the concept of decoupling. This is why decoupling must be actively practiced. When you learn any new composition, there will always be some coupling until you practice it out. The worst type of coupling is the one acquired during practice, if you practice with stress or try to play something that is too difficult. During the intense efforts needed to try to play difficult material, a student can incorporate any number of unnecessary motions, especially during HT practice, which will eventually interfere with the playing as the speed increases. By getting up to speed HS, you can avoid most of these HT coupling mistakes. Another important use of the body is in playing softly or forte. Truly loud and authoritative sound can be generated only through the use of the shoulders. The body should lean forwards and the weight of the shoulders should be used. Thus the sound is produced by a larger mass, and the audience can hear this. We all know that F = Ma where “F” is the force applied to the key drop, “M” is the mass of the finger, arm, etc., and “a” is the acceleration of the key drop. Since you can humanly accelerate the finger tip by only a certain amount, the mass M determines the force because M can be made very large by adding the body and shoulders. With this larger force, you can drive the hammer to a higher velocity and with more hammer shaft flex, compared to if you just used the arm. A hammer hitting the strings with more force and shaft flex stays on the strings longer because it must wait for the flex to unwind before it can bounce back. The larger force compresses the hammer felt more, which also contributes to longer residence time on the strings. The longer residence causes the higher overtones to be attenuated more efficiently (because they have more chances to escape through the hammer, etc.), resulting in a "deeper" tone. In other words, with more mass behind the key drop, you transfer energy to the strings more efficiently. A golf ball bouncing off a concrete wall at high speed will leave the wall with almost all of its initial kinetic energy, which means that it transferred little energy to the wall. It also creates a high frequency pinging sound. A heavy wrecking ball, on the other hand, has a larger mass, and although it may be traveling more slowly than the golf ball, can transfer enough energy to destroy the wall. It also tends to create a deep, roaring sound. Although the piano hammer cannot change its mass, the shaft flex produces an effect similar to that of a larger mass. This is why teachers tell students to "press deeply into the keys" in order to produce a loud, authoritative sound. This motion results in maximum mass behind the key drop, and maximum hammer shaft flex. The shaft flex is maximized by providing the greatest acceleration near the bottom of the key drop, just at the time when the jack releases. If you don't "press deeply" you tend to stop the acceleration before reaching the bottom (this need to accelerate at impact is the reason why the “follow through” is so important in golf). Note that the shaft flex starts to unwind as soon as the hammer goes into free flight, even before the hammer hits the strings. Because of this effect, good piano tuners do their utmost to minimize the let-off distance when regulating the action, so as to provide maximum tone control. Therefore, if a few hammers stick in their upper position right after your tuner regulated the piano, don’t be angry at the tuner because s/he made a much greater effort than most tuners to “get it just right” by minimizing the let-off distance. Keep exercising those notes, and the leather at the knuckle will compress and those notes will soon start to play normally. The body is also used for playing softly because in order to play softly, you need a steady, constant platform from which to generate those small, controlled forces. The hand and arm, by themselves, have too many possible motions to serve as a steady platform. When attached securely to a steady body, you have a much more stable reference platform. Thus the soft stillness of the pianissimo should emanate from the body, not the fingertips. And in order to reduce mechanical "noise" from extraneous finger motions, the fingers should be on the keys as much as possible. In fact, feeling the keys provides another stable reference from which to play. Once the finger leaves the key, you have lost that valuable reference, and the finger can now wander anywhere, making it difficult to accurately control the next note.