Sound from the piano is created when the performer's mind/body mapped* fingers rest on the key surface, and there is mindful application of: Force = Mass X Acceleration
Force equals the performer's intended acceleration times the combined mass of both:
1) the mechanical action of the keys (this mass is "fixed" in every piano) and 2) the performer's intended body mass. (the performer varies this mass)
1) Every acoustic piano, with its inward mechanism, is basically the same machine, some actions certainly preferred over others. The mass of this mechanism is fixed for each piano, with obvious distinctions felt, when comparing the lowest keys, with biggest hammers, to the highest keys, with the smallest hammers, including the middle keys with their hammers.
The performers body mass, I believe, includes from lightest through heaviest body parts -fingers, through hands, forearms, upper arms, shoulders, upper chest/back. Movements for all of these parts physically originate from the Sterno-Clavicular joints, at the heart center of the body.* From here, the whole shoulder girdle freely moves up/down and forward/backward when 20% of our core power stabilizes the braced torso. When these shoulder movements are combined, forward/backward circles of the whole shoulder girdle become possible. The shoulder girdle factors into determining the amount of mass the performer can intentionally release into fingers resting on the key surface. With awareness of how light or heavy the fingers are resting on the key surface included in the mind's eye, the performer accelerates the key with the intended speed and mass, through of the point of connection with the mechanical action of the key (i.e. the little "bump" felt about half way between the key surface and key bed), forcing the hammer to strike the string and creating the intended sound.
Piano Fitness Postural Fundamentals
Exploration Exercise 1:
Sit as you normally sit on the piano bench. Place all 10 finger on any 10 keys, where both arms are most confortable. Close your eyes, let the mind's eye watch the breath for several cycles.* Begin to be aware of your feet on the floor, hips on the bench, fingertips on the keys. Take several more full breaths. Allow the fingertips to feel heavier on the key surface and then lighter on the key surface. Explore the extremes of your heavy and light feelings while observing several more full breaths. Observe where changes in the body are occurring when exploring your lightest and heaviest sensations. How much, if any, is originating from the sterno-clavicular joints?
Next, allow the 10 fingers to rest on the keybed in the same comfortable arm position, while taking more breaths and repeating the light/heavy sensations. Increasing awareness of your heavy/light extremes at both key surface, before the sound is created, and on the key bed, after the sound is created will enhance sound production, and must be included for every note/key/finger played. Lastly, let lightly resting fingers feel heavier on the key surface until the keys, under the fingers, depress and the 10 fingers are resting on bumpy points of mechanical connection above the keybed but below th.e key surface. If able, allow the heaviness to release through the connection bump to rest the 10 fingers on the key bed ligher to heaviest. There may or may not be sound produced from this final release.
Including awareness of how this "sweet spot" bump is accelerated with intended varied mass
is best controlled with the developed sense of touch from the fingertips resting at the key surface. Including the sense of touch increases brain activity and can enhances memory.
Awareness of finger/key connection, physically initiates intended sound. With this connected awareness, the mind, intending both mass and acceleration, forces the hammer to hit the strings and the intended sound is created and communicated to the listener(s).
* email request for "Mapping the Mind/Body Connection" PDF, for more information.