A second typical characteristic of pianistic movement s is repetition, both 1) absolute and 2) relative : repetition without further displacement , and repetition of one part while the movement as a whole shifts along the keyboard. This complexity is at the bottom of all but the most elementary five-finger positions. The distal^[1] part of the arm, for example, the fingers or hand, is performing a smaller and usually more rapid movement, while the proximal^[2] parts of the arm: fore-arm or upper arm, are moving in a wider range and usually at a slower rate. The act ivity at the various joints, therefore, is neither equal nor devoted to the same end. Instead, it usually consists of a slow, fairly continuous movement in the larger joints while the smaller joint s are engaged in more rapid discontinuous movements.

Absolute repetition is found in such passages as the repeated octaves of Schubert's Erl-King, the accompaniment of Chopin's Berceuse, the left hand, second sect ion of Chopin's F sharp major Impromptu, any sustained trill. In the analysis of such movements, I found a pronounced tendency on the part of the player to get away from the pure repetition in all rapid forms by shifting some other part of the arm than the part directly engaged in tone-production. This attempt, not always entirely successful, was so general that some physiological necessity must have prompted it . The necessity is probably muscular fatigue. In other words, rapid repetition tends to produce fatigue by over-shortening the period of chemical readjustment between movements. When the player begins to move a second part of the arm in addition to the part actually playing, he alters the direction-relationship between the parts. As a result he alters the muscular coordination somewhat, for the position of the muscles, their points of origin, extent, and their points of insertion are such that a skeletal part cannot be changed without affecting the mechanical pull of muscle, since the tendon is joined to the bone. A muscle acting in a certain way with the moved part in a certain position, will act in a different way with that part in a different position.
Conversely, as a part is moved, the action of muscles often shifts from one group to another, some acting at a better mechanical advantage. This has been explained in detail in the analysis of muscular action, where numerous concrete illustrations have been given, and it will be further analyzed in the study of the various touch-forms.

By adding a slow movement of larger muscles to the rapidly repeated movement, the player changes the movement from one of absolute repetition, to one of relative repetition. With this he eliminates absolute muscular repetition and consequently, in the case of rapid movements, reduces the danger of early fatigue. Let us take, as an example, rapidly repeated octaves. These are usually accompanied by a slow raising and lowering of the wrist. The muscular coordination producing the octave, with the wrist in a low position, is not exactly the same liS thllt used when the wrist is in a high position. Nor is it entirely the same for any change in wrist-position.
For each stroke, therefore, a small increment of unused muscle is available, while at the same time, a similar increment of used muscle is permitted to recuperate. The physiological advantage of this procedure is obvious. At the same time we must not forget that it has also a decided psychological value, in substituting a higher unit at a slow repetition for the lower unit of rapid repetition.

Once again such a coordination is opposed to the doctrine of fixation or isolation. It has a disadvantage on the mechanical side because, at first, it increases the difficulty of dynamic control. The wave effects of the top record show the uncalled for dynamic variations resulting from the blend of the wrist movement and the hand-stroke. It takes considerable practice to eliminate the variations and yet retain the wrist-movement .

[1]distal: situated away from the center of the body or from the point of attachment.

[2]proximal: situated nearer to the center of the body or the point of attachment. "the proximal end of the forearm"