The escapement mechanism in a piano is what allows the hammer to fall back quickly after striking a string, allowing the string to resonate freely.
Without it, the hammer would remain pressed against the string until the key is released, muting the note. The double escapement action allows a pianist to press the same key quickly in succession, as it doesn't require the key to be fully released before being pressed again.
Aiming or directing energy with the Key
The aiming or directing of the Key, comprises three points :
We must aim the key, so that its full speed is reached at the moment that the hammer-end is in communication with the string.
This is the moment that the escapement[1] permits the hammer to rebound with the string the moment that we can hear the beginning of the sound when we listen for it.
We must cease to apply energy against the key at that same moment, with the exception of the slight impact of weight that is required in tenuto and legato in order to prevent the key from rebounding.
We must determine in which manner the required speed shall be reached, for if the total energy is applied suddenly, then the result is a "brilliant" but "short" tone. If it is instead applied gradually, then we shall obtain a true "singing" or "sympathetic" tone of good carrying power.
1. Key, 2. Capstan, 3. Wippen Heel, 4. Wippen Body, 5. Wippen Flange, 6. Wippen Flange Rail, 7. Jack, 8. Repetition Lever, 9. Hammer Knuckle,
10. Hammer Shank, 11. Hammer Head, 12. Hammer Flange, 13. Hammer Flange Rail, 14. Lever Lift Felt, 15. Damper Lever, 16. Damper Assembly,
17. Drop Screw, 18. Jack Toe, 19. Let-Off Button, 20. Let-Off Rail, 21. Hammer Tail, 22. Back Check, 23. Back Check Wire, 24. Repetition Lever Flange,
25. Repetition Spring, 26. Hammer Shank Cushion, 27. Rep Lever Regulating Button, 28. Jack Regulating Button, 29. Spoon, 30. Action Bracket
This detailed labeling provides an overview of the different parts involved in the action mechanism of a piano, each essential for the instrument's functionality.
Time-place and Tone-value
The first lesson in key-treatment which must be learned is that the time-place and tone-value of every note must be musically realized and intended. The second lesson is that the key must be aimed to culminate its speed in sound, at that very moment. These two things must coincide. We must therefore aim or direct the key into speed and direct its increase in speed during its short journey, so that we shall compel the string to begin its sound at the very instant that the sound is musically due. We shall then have correctly obeyed our time-sense, and our tone-sense. Having thus definitely compelled tone-production to fulfill our musical conception, a clear and definite impression will consequently be conveyed to the listener. For we shall have succeeded in transmitting to the audience the same musical impression with which we ourselves were influenced.
[1]escapement: The escapement is the mechanism in a grand piano that allows the hammer of a key to fall away from the string after it is struck, making it easier to play soft notes repeatedly. When you softly press a key on an acoustic grand piano, you will notice a certain click or soft "catch" toward the end of the range of motion.
