In order to study the fundamental touch in piano playing, the physiological mechanics of the player and the kinetic mechanics of the swing-stroke system in the piano need to be studied. Equipment for analyzing and measuring the intensity of the swing-strokes has been developed to study the fundamental touch in piano playing. This equipment measures the velocity of the hammer and indicates the relationship of the intensity and the velocity of the swing-strokes. The tone-volume depends on the amount of kinetic energy which the player spends instriking the key. The kinetic energy is in direct proportion to the mass set in motion and is the square of the velocity. The mass set is always constant and the energy depends only upon the velocity of the hammer. Thus it is possible to analyze the tone-volume by measuring the velocity of the hammer. Two methods of swing-strokes were set up to analyze the movement of the swing-stroke. Two experiments were performed: (a) static swing-stroke in which the height of the swing-stroke was fixed and the weight was changed and(b) dynamic swing-stroke in which the weight of the swing-stroke was fixed and the height was changed. Experiments with the swing-stroke were made by a skilled pianist. The control system of the intensity of the swing-strokes is discussed.