Introduction to Action and Reaction in Piano Playing

Action and Reaction

1. The effect of finger impact upon the joints of the arm comprises the basic operation of mechanical principles used in piano playing.
2. This principle of action and reaction states that the forces acting on any point at rest are equal and opposite.
3. When the finger-descent is brought to a stop by key resistance the upward acting force of this balances the downward force of the finger.
4. In a finger stroke, the descent of the finger is caused by a decrease in the angle which the finger makes with the hand.
5. This decrease in the angle results from a contraction of the flexor muscles.
6. The extensors raise the fingers up from the keys, the flexors lower the fingers to the keys.

Important Characteristic of Physiological Movement

1. When the descent of the finger is suddenly stopped by the piano key, the effect of the muscular contraction is still to decrease the angle referred to .
2. Since the fingertip cannot descend further, the only remaining way in which the angle can be reduced is by raising the hand knuckle.
3. The fingertip becomes the fulcrum and the hand knuckle the moving part.
4. Before the finger-tip reaches the key, the hand knuckle (first phalanx and metacarpal bone) is the fulcrum and the fingertip is the moving part.
5. This interchange of mechanical points is an important characteristic of physiological movement.
6. It is best observed in gymnasia. In ''chinning'' a horizontal bar, the same muscles contract, but here the hands are the fulcra and the contraction of the biceps lifts the entire body until again the shoulders are brought close to the hands.
7. This dual effect may be present in any other contraction, and as a result the same muscular contraction may produce different movements.
8. If the two finger joints are flexed, the finger-tip will approach the palm of the hand.

Resistance introduced against Finger Flexion

1. If a resistance be introduced against this flexion, thus making movement at the fingertip impossible, the same contraction of the muscles will bring the fingertip close to the palm by pulling the 1)hand, 2) forearm, and 3) upper-arm forward.
2. If the hand-arch be held firm, the impact of the fingertip upon the key will result in an upward reaction at the wrist.
3. The force manifested at the wrist will be equal and opposite to the force of the descending finger-tip.
4. Even in a very light touch, some of this reaction will be present.
5. If the hand-knuckle is relaxed the reaction will manifest itself as soon as the key is touched by the finger.
6. Tone is introduced until the key has almost been completely depressed (the point of hammer escapement).
7. Consequently, in order to obtain the proper force effect, the hand knuckle must be kept fixed as a fulcrum.
8. In a relaxed joint, part of the force which is acting upon the key is spent in moving the relaxed joint itself.
9. Part of the force is lost for work at the fingertip.