The piano has an undisputed father: his name is Bartolomeo Cristofori, born in Padua, Italy on 4 May 1655.
He was in the service of Prince Ferdinando de' Medici, in Florence, as harpsichord maker, from 1688 or 1689. In reality it would seem that the piano was conceived by Cristofori when a group of Florentine nobles discovered the flaws of the harpsichord.
Documents set "two years before the Jubilee" (the Jubilee of 1700, and therefore to 1698) the beginnings of the experiments conducted "at the behest of the Grand Prince Ferdinando" and to 1700 the very first description of a "Harpsichord of Bartolomei Cristofori, of new invention, who makes the piano and the forte”.
At the Medici court discussions took place during which - testimony of the composer and poet Giovanni Maria Casini - it was argued "how we can render on the instruments the talk of the heart, now with a delicate touch of an angel, now with a violent irruption of passions", observing at the same time that "the harpsichord does not complete all the expression of human feeling". The intellectuals of Florence actually wanted to reconcile two irreconcilable factors: the advantages of the machine and the continuous control of sound.
An utopia was born, a chimera, in search of which the brain of Bartolomeo Cristofori was set in motion. Cristofori thought of a keyboard instrument, not with air (like the organ), or with plucked strings (like the harpsichord) or rubbed (like the clavichord), but with struck strings. He kept intact the structure of the harpsichord (a series of strings stretched on a wooden frame and whose vibrations were amplified by the vibration of a thin wooden top, the soundboard), replaced the saltarelli with leather-covered wooden mallets which he called hammers, and he called the new instrument "gravicembalo (or harpsichord) with piano and forte".
Very exact denomination. The instrument was a harpsichord: the performer determined beginning and end of the sound and did not have the possibility to influence its pitch. But it could affect the intensity, soft and loud, which is impossible on the organ, almost impossible on the harpsichord and possible, however too limited and risky, on the clavichord.
To get to this point, Cristofori had to solve a single but enormous problem: a string struck by a hammer sounds softer or louder depending on the smaller or greater amplitude of its oscillation and therefore the speed reached by the hammer at the moment of contact. Using a system of levers it is easy to make the speed of the mallet, or hammer, depend on the speed at which the key is lowered. But when the mallet is operated by hand, the performer withdraws it immediately after the hit because, otherwise, the contact with the mallet would prevent the string from vibrating.
Cristofori had to reconcile the two principles of percussion and the cessation of sound: both should have been controlled by the key. He therefore kept the last two levers separate, providing them with two opposing tips: the escapement. The tip of the penultimate lever pushes the corresponding tip of the last lever upwards. Since the two levers are pivoted and arranged one against the other, and therefore moving in a opposite circular direction, the contact ceases after the push: the lever that carries the hammer falls due to the force of inertia immediately after the impact with the string and the sound can last until the player, by letting the key return to its resting position, pushes the felt pad, or damper, which was already part of the harpsichord mechanics, against the string.
Cristofori also added a spring to the tip of the penultimate lever to accentuate its movement, and supported the hammers with crossed silk threads, to stop their rebound after the fall.
Its mechanics were elementary but perfect.
Bartolomeo Cristofori had done everything that could be done.
Not what his noble interlocutors had dreamed of, because his instrument could play “piano and forte”, but without the sound being able to remain constant or increase after percussion. As in all percussion instruments, the intensity decreased immediately, giving rise not to a true continuous "human feeling", but to intermittent impulses, almost a sound divisionism.
The "gravecembalo with piano and forte" was described by Scipione Maffei in 1711 in the "Giornale dei Letterati d’Italia". He sets out the aesthetic reasons for the invention with extreme clarity: “Everyone who enjoys music knows that one of the main sources from which the experts of this art derive the secret of delighting the listener is the piano and the forte”.