Rotation Cessation

Now, the trouble is, if this exertion inwards (momentarily required to help the thumb) is instead continued at full strength, then the basis for the action of the other fingers is taken away from them and the sense of balance is lost. Continued pronation towards the thumb creates an antagonistic muscular pull, which prevents fingers 2 through 5 from performing their work. Because of this incorrect application of exertion inwards, thousands of futile exercises have been designed to overcome this supposed "weakness" of these fingers.
These supposed "weak" fingers are rendered quite "strong" the very moment we analyze the necessary single and double rotation of a passage.
Note: Such exertion towards the thumb may be so slight that we are likely to overlook it. Any exertion, in the wrong direction, will inevitably impair the effectiveness of the next finger used. Be sure to avoid a rotatory exertion in the wrong direction, even from the "weak" rotation muscles. Because certain pianists do not comprehend this point, certain players have come to believe the "weakness" of the fourth and fifth fingers at the piano.
Remember, these fingers are rendered helpless so long as you continue a strong rotational exertion towards the thumb after it is played, and thus deprive those other fingers of the necessary basis for their action against their keys; Fingers four and five are instantly transformed into "strong" fingers, provided that when you wish to use them you are careful to eliminate any residue of unneeded rotatory exertion towards the thumb. The forearm of the keyboardist must remain rotationally free.

With the hand lying loosely on the keyboard the hand will quite naturally roll upward onto its side (with the little finger as a pivot) when you cease the slight rotatory exertion towards the thumb. Now, if at that very moment, however, you sufficiently exert the little finger, it will act as a strut, and will thus prevent the hand from rolling upward and your hands will be "balanced on the surface of the keys".
You cannot see any rotatory movement, but you can feel the stress in the direction of the little finger, and how this is thereby helped. For soft notes, cessation of all the rotatory exertion towards the thumb hence suffices to give the little finger the necessary basis for its work in sounding that soft note. When more tone is required, then you must (in addition to ceasing the exertion towards the thumb), also add a rotatory exertion towards the little-finger side, to enable you sufficiently to exert that finger.

Be sure to realize through experiment at the keyboard, that if you cease the exertion inwards (towards the thumb) this will leave the forearm outwards (towards the little finger), and that this tumbling-over tendency of the forearm, thus rotatory-help caused by relaxation, can provide for more tone from your little finger.
For greater tone, however, you must, in addition, exert the forearm outwards, although this rotative exertion is not necessarily displayed as movement, neither in this case nor the former one. As everywhere else in technique, movement or its absence is no criterion for determining the correctness of a motion.
For instance, if you cease the rotatory exertion towards the thumb (as just discussed), the hand would naturally supinate towards the fifth finger, but this rotation will be prevented if you accurately time a sufficient exertion of the little finger (or other finger) at that moment. In this instance, you then have only a finger movement with the key. The rotational relaxation is not in the least disclosed to the eye.
That is, the rotatory change towards the little finger will not be seen, if you hide it by a sufficient exertion (and movement) of the little-finger, or fourth finger at that moment. On the other hand, the exertion of the finger itself will be hidden, if you outbalance it during key-descent by a greater exertion (and movement rotationally) of the forearm. You then have rotative movement (or "Rotation-touch") in place of finger movement (or "finger-touch") with the key. In slower passages (as previously said) actual rocking or rotation may optionally be employed, but in quick passages there is no time for such movement. In summary, forearm-movements are usually preferable in quick passages, using the proper individual forearm-stresses invisibly applied, along with the exertion of each individual finger.