The piano sound whose harmonics and noises are controlled.
The great Italian pianist Ferruccio Busoni once wrote about the difference between the sound "of the piano" and the sound "of playing the piano".
What is meant by "pure sound"?
A "pure sound" is a sound whose harmonics and noises are controlled .
But how can we create a "pure sound"?
Let's start from the beginning explaining the basic aspects of piano playing: to many it will seem trivial, but perhaps not at all. I apologize to the reader for the arid but necessary description of the following technical facts .
The timbric variables of the piano depend on three factors:
- the crushing of the felt covering of the hammer in the impact against the string
- the noise of the finger impact with the key
- the noises of mechanics
The touch can be:
- touch for percussion (the finger is not in contact with the key)
- touch by pressure (when the key is unbalanced the finger is in contact with the key)
The unbalancing action of the key can be made:
- by finger only
- by finger and hand
- from finger, hand and forearm (with or without forearm rotation)
- from finger, hand and whole arm (with or without lifting of the elbow and / or shoulder)
The direction of the key attack can be:
- vertical
- semicircular
- longitudinal (towards the lid or towards the end of the key)
- tangential (to the right or to the left)
The elements that influence the acceleration of the key are the following:
- speed
- distance
- mass
The crushing of the felt covering depends on the speed of the hammer which causes the formation of certain harmonics.
Young's law explains how there is always a timbric difference between the piano and the forte; it is a fact that the hammer proceeds at a slower speed in the piano and at higher speed in the forte.
But the science of touch can modify this result.
The hammer starts with zero speed and reaches the impact speed thanks to acceleration.
The speed of impact can be reached by means of different degrees of acceleration.
Therefore to obtain a certain type of sound the pianist has to wonder at which speed, distance, mass and direction to unbalance the key.
The key is a first-order lever: while it goes down on one side it rises on the other.
The opposite side of the key is connected to a rod with a felt-covered hammer, which receives an impulse and rises.
The key disengages from the rod before the hammer meets the string, and there is a stretch where the hammer comes to hit the string, thanks to the momentum received, and then falls back.
Sound is the summation of an infinite number of harmonic sounds.
During vibration there are as many knots in the rope as there are harmonics.
Young's law says that the excitation point of a string cannot form a knot.
When the felt arrives against the rope it is crushed, and it strikes it at an eighth of its length.
At the point of contact of hammer with string the harmonic 8, consonant, cannot be formed.
But the crushing of the felt can also cover a seventh and a ninth of the length of the string: the harmonics 7 and 9, dissonant.
So, depending of how this crushing occurs, we try to avoid or not the presence of the seventh and ninth harmonic.
The modification of the harmonics represents the modification of the timbre.
The presence of noise in the sound compromises its purity.
The set of noises is considered from:
- noise given by the way finger impacts (with the fingertip, with the tip or with the nail)
- noise given by the way key is released (it depends on how quickly it is traced)
- pedal noise (depends on how quickly it returns to the normal position).
The slower the release of key and pedal the less noticeable will be the movement noises of the mechanics.
The finger's impact noise will be muffled in relation to the amount of finger pad that will be used.
All noises are distinguishable from a distance of few meters, after which they become an integral part of the timbre.