Why does the keyboard have the shape it has?
The shape of the keyboard depends on the shape of the hand and on the evolution of Western music.
Up to a certain point the keyboard changed according to the evolution of music, then the opposite happened and it was music that, adopting equal temperament at the beginning of the eighteenth century, showed that it did not want to give up the advantages of a keyboard that could not be further modified.
The voices of women and men, singing the same melody, do not emit sounds of the same pitch: the number of vibrations per second of the female voice is double that of the male voice. This one-to-two ratio, called octave, has remained unchanged from Greek antiquity to today, while the intermediate relationships have historically evolved, leading to the birth of various systems.
At the end of the seventeenth century the number of intermediate ratios in use was such that the keyboard was no longer able to reproduce them all.
Attempts to modify it were in vain because the ratio between hand opening and finger width, with respect to the width of the key, could not be changed if not losing much of the practical advantages that the keyboard offered.
The compromise solution was found with the adoption of equal temperament, that is, the artificial system that adapts the theory to the keyboard, establishing with a mathematical formula (12th root of two, 11th root of two, 10th root of two, etc. ) the intermediate ratios, equal to the number of keys, twelve per octave, possessed by the keyboard.
The line of the widest, longest and lowest (usually white) keys corresponds to the so-called diatonic scale.
The line of the narrowest, shortest and highest keys (usually black) correspond to chromatic semitones.
The low keys are easily touched by all the fingers, placed on the keyboard in the position that the hand assumes roughly in rest, when walking.
The high keys are easily reached by the longest fingers - index, middle, ring finger - with a simple unfolding movement.
The performer can thus perform a series of operations almost equal, in number and complexity, to those of an orchestra.