The mechanism of any musical instrument must establish in all cases a law for the application of the energy to be used upon that mechanism. When energy is correctly applied, the machine or mechanism should give back an equivalent of work done; but if the energy applied is lacking or weak, then the results will be the same.

As every musical instrument has that part of it which is to be played upon. Constructed with reference to the shape and motions of the hand. Compare the keyboard of the piano with the different fingerboards of violin, cello, double bass, or with the key area of the several kinds of wind instruments.

Of all musical instruments, the piano is probably the one which calls for, in the performer, least departure from a position already natural to him. The attitude of sitting is allied with one of the hands and arms more natural and easy than that used in playing on any other instrument.

The violin demands a more constrained position of arm and wrist than is ever needed for the piano. The organ, in consequence of its requiring a great amount of work from the feet as well as from the hands, allows the performer a much less steady position and balance than does the piano.

The harp, from its peculiar form, necessitates a position of some constrain both of arms and body. And all wind instruments, from their necessarily interfering with any free movements of the head and arms, are also less adapted to afford perfect ease of posture.

The piano, on the contrary, is unusually well suited to the natural movements of the body. Its keyboard is positioned so that it allows the arms and hands complete freedom of motion in every direction. The position of the hand most suited for playing on the keys considered as levers, is the same position into which it falls when the arm is allowed to hang naturally by the side. The angle of the elbow, when the hands are on the keys, is also that best suited to facilitate the natural movements of the muscles of the hands and arms.

In applying any two mechanisms to one another, that which has the less power of adapting itself to the other will necessarily be first examined with regard to its inherent conditions of motion. In the present instance, the hand must accommodate itself to the keyboard of the piano. In order to do so, fully and constantly, it must take note of the limit of the capabilities of the instrument.

These capabilities must be taken full advantage of, but must never be overtaxed as no overtaxing of the piano's mechanism can take place without involving an overtaxing of the muscles of the hand and arm.

With regard to the key itself, it will be seen that its motion is of the simplest nature. When acted upon by any sufficient weight, the key moves downwards, and when freed from this weight it moves upwards to its previous position.

This simple downward and upward motion is its only method of acting upon the hammer and damper with which it is connected. Regarded as a lever, this simplicity of action will be considered all that is necessary for the key. The duty of the hand, in using this lever correctly, is therefore to push it downwards.

When a piano key is pressed down, it sets in motion the hammer and the damper. It will be necessary to look at each of these actions separately.

The hammer at the moment of the key's descent is pushed up against the string and falls back instantaneously; its work is then finished. The period of time during which it is in contact, with the string is of the shortest duration, the act of percussion being momentary and accomplished instantaneously.

The second duty of the key is its action on the damper. It has already been stated that, the piano key is still working until the instant that it is released; it's still working because it's preventing the damper from touching the string, thus allowing the tone to continue sounding.