[in this article i'm going to report some observations on piano key actions]
In the era of digital pianos, there's a common grievance about how digital piano's key action feel is nowhere like acoustic pianos. The reason for this is simple. On an acoustic ('real'
piano, the key action mechanism are hammer based. That is, there is a series of intricate mechanical apparatus, such that when a key is pressed, a seasaw (fulcrum) is pushed to cause a hammer to jack up and hit the string, which vibrates and makes a sound. If the key is pressed hard (quick), it eventually cause the hammer to hit the string strongly. Similarly, if the key is tapped lightly, the hammer hits the string mildly, causing sound of less volume. However, if the key are pressed too softly, there's not enough force to jack up the hammer. Thus, one has to hit the key with some minimal pressure or velocity to make a sound.
also, because the whole physical mechanism involves elaborate fulcrums & levers & spring & dampers & hammer etc, there's this intricate tactical sensation when playing on an acoustic piano. Namely, the resistance from pressing the keys are somewhat non-liner with respect to velocity level. If pressed too softly or slowly, no sound are made as there are not sufficient pressure to fly the hammer. If pressed very hardly, one can feel the momentum of the hammer, where a loud sound will be made without having to press the key all the way down. By resting a finger on a key and play it like a child plays seasaw, one can feel the varying weight of the hammer on the other side.
In contrast, modern digital piano's keyboard has very different feel to them. Because the musical instrument is electronic, there's no string to hit, and no need for elaborate hammer or leveler mechanism. All that is required to register the sound is a device that measures velocity or pressure of the key being pressed. Thus, digital piano's key mechanism are often such that the there is a linear relationship between velocity & volume: The harder you hit the key, the louder it sounds, and that's it. The resistant of the key is also uniform, unlike that of acoustic piano. As if there is a soft marshmallow underneath the key, where regardless how you press the key or whether it is already halfway depressed, its resistance is the same. Scientifically even, or artistically inert, depending on your point of view.
One easy way to realize the performance effects of these two actions is trying to play scale in the softest manner possible. (ppp pianissimo) On a digital piano, this is easy to do. On an acoustic piano, it takes more skill to perform, because one needs to apply just the right pressure to get the hammer flying but at the minimum speed. If the fingers are not well trained, then on some notes there'll be no sound, while others will be noticeably loud.
