Briefly exert your finger and hand as fully as you would like during key-descent to attain that duly required acceleration just up
to the point of sound, and then completely cease all that work, and hold on to the key solely by that gentle elastic action of
finger and hand which leaves knuckles, wrist, and fingers quite elastic. In other words, exert the strong flexors both of the finger and hand during key-descent, but hold the notes solely by using the weak muscles of the hand.
Note: Remember that excellent example of the oyster, quoted by John Hunter, and it should not prove to be difficult for an intelligent keyboard player to learn to sound a note correctly, and to hold it correctly afterwards after the sound has been produced.
This law of holding lightly (by means solely of the "weak" finger muscles) applies equally, whether you hold the notes fully
depressed (as for Tenuto
[1] or Legato) or whether you hold the notes instead at their surface-level, as in staccato, and in all light
agility passages.
[1]
flexors: The flexor carpi radialis is a muscle of the forearm situated medially to the pronator teres muscle. It originates from the medial epicondyle of humerus and descends inferomedially to the midpoint of the forearm, where it extends into a long tendon.