Incorrect versus Correct Key Movement

The muscular process of sounding a note at the piano is, however, by no means a simple act as it appears to the eye. To begin with, it should never be in the nature of a blow upon the key, even though it may look like that. This does not constitute good playing even though the player himself may imagine that he is hitting the notes down. Always realize, that 1) the action of moving to a key and 2) the action of subsequently moving with that key during its descent, should always be two quite distinct things. These two distinct motions are fused into one motion by achieving a sense of continuous motion .

You may reach the key either by a movement of the arm, hand or finger, but whichever component you employ, and however swift the movement may seem to the eye, the true tone-producing action is not applied until after you reach the key when playing correctly.
Tone-production is always in the nature of a "follow-on" pressure upon the key after it is reached and during key-depression. This tone-producing pressure must increase in intensity during key-descent. This application of physical energy becomes useless, as far as tone-production is concerned, the moment the key is in its final state, and it should therefore cease immediately. The so-called "finger-touch" may appear to the eye as if the fingers were used "like little hammers". In reality there never is any such real knocking action. To the eye, the finger of a good player may seem to descend upon the key fairly swiftly, but its exertion upon the key (and with it during its descent) is always a thing added after contact. You must feel the surface of the key before you set in motion.