Preserve the quality of the sound in piano songs by pressing keys all the way down to the bottom of the keybed and play with loose fingers and arms.
Have you ever experienced attempting to play a key in pianissimo but ended up not making a sound because you were over soft? Or played a phrase fortissimo but coming off as noisy instead of elegant? If you have, like I have it was because the sound lost its quality due entirely to my own doing.
So what went wrong?
If I were to strike the keys from a height, I do not have control over the outcome of the chords or octaves I am trying to produce. All kinds of weird, unintended percussion effects appear. They lose the quality in sound.
To get a rounded loud (forte or fortissimo) sound, I get my fingers to make contact with the keys without pressing. Once they have touched the surface of the keys, only then do I use the energy from my upper body to press on them. I do so as if I was pushing backwards, as if shoving the piano forward through the wall behind it.
Be sure to press all the way down to the bottom of the keybed. Playing loud, this is seldom a problem. Having reached the bottom of the keybed, cease the effort just switch it off. Release whatever force you were exerting – to be at ease, until you begin to play the next note.
Another tip I can offer about playing forte or fortissimo is, although in the score the marking implies the phrase be played loud, to get the desired result does not require playing every note in the phrase loud. Recognize the strong base note, usually the top note within the clusters of notes in the phrase and play only those notes loud. Less so, in the middle notes.
The risk of notes not sounding when playing soft (piano or pianissimo) can be mitigated by applying the same principle. Which is to press all the way down to the bottom of the keybed. Play a note with the level of sound you wish, thereafter palpate the sensation of wood beneath the keys by making a little contact with their bottom.
More on it later, just briefly for now, realize that the piano is played with the wrists not the fingers. Having said that though admit that strong fingers are indeed needed, to preserve the quality of the sound you make on the piano.
Thus, before I play the Rondo Alla Turca, I warm up my fingers practicing the scale of A minor. My goal is not to execute the scale to perfection but to loosen the fingers and arms. So, I do not mindlessly repeat the scale which is pointless not to mention hastens the losing of interest in the exercise, instead I lift each finger high with each strike of the keys to feel the stretch. I would press the key down all the way to the keybed, releasing the effort once I reach it. This is repeated when I play the next note in the scale.
Making use of the same A minor scale, I modify the exercise to work on my weakness by putting all 5 fingers beginning with the thumb on D resulting in the 4th finger being placed on G#. Holding the 3rd finger down on F, keeping it pressed all the way to the bottom of the keybed, I then play the other notes around it.
Later, I would hold the 4th finger down on G# and play the other notes around it. Followed by holding down the combination of the first and fourth finger on D and G#, even a combination of the second and fourth finger on E and G# while playing the other notes around them.
The reason I chose to do this with the scale of A minor is because it has a black key in it. Regular piano songs would always have black keys in them so it is best to design my exercises to resemble them. The A minor scale is a good place to start because it has only one black key.