The piano first known as the pianoforte evolved from the harpsichord around 1700 to 1720, by Italian inventor Bartolomeo Cristofori. Harpsichord manufacturers wanted to make an instrument with a better dynamic response than the harpsichord. Cristofori, the keeper of instruments in the court of Prince Ferdinand de Medici of Florence, was the first to solve the problem.

The instrument was already more than 100 years old by the time Beethoven was writing his last sonatas, around the time when it ousted the harpsichord as the standard keyboard instrument.

Bartolomeo Cristofori

Cristofori was born in Padua in the Republic of Venice. At age 33, he was recruited to work for Prince Ferdinando. Ferdinando, the son and heir of Cosimo III, Grand Duke of Tuscany, loved music. There is only speculation as to what led Ferdinando to recruit Cristofori. The Prince traveled to Venice in 1688 to attend the Carnival, so perhaps he met Cristofori passing through Padua on his return trip home.

Ferdinando was looking for a new technician to care for his many musical instruments, as the previous worker had passed away. However, it seems possible that the Prince wanted to hire Cristofori not just as his technician, but specifically as an innovator in musical instruments. During the remaining years of the 17th century, Cristofori invented two keyboard instruments before he began his work on the piano. These instruments are documented in an inventory, dated 1700, of the many instruments kept by Prince Ferdinando. 

The spinettone was a large, multi-choired spinet (a harpsichord in which the strings are slanted to save space). This invention may have been meant to fit into a crowded orchestra pit for theatrical performances while having the louder sound of a multi-choired instrument.

The Age of the Piano

From 1790 to the mid-1800s, piano technology and sound was greatly improved due to the inventions of the Industrial Revolution, such as the new high-quality steel called piano wire, and the ability to precisely cast iron frames. The tonal range of the piano increased from the five octaves of the pianoforte to the seven and more octaves found on modern pianos. 

According to thoughtco.com