In his lifetime Bach was famous as an organist and harpsichord player, and churches invited him to test and open their new organs. He wrote his keyboard music for the organ, the harpsichord and the clavichord. The piano was still a new invention, and the modern concert grand did not yet exist.
The three instruments sound very different. On an organ, air is blown through pipes. On a harpsichord, pressing a key makes a small quill pluck the string, so the player cannot make one note louder than another by touch. On the clavichord, a small brass blade strikes the string and stays against it, which allows fine shading but is too quiet for a hall. The piano, invented by Bartolomeo Cristofori in Florence around 1700, let players play both soft and loud; its full name, pianoforte, means “soft-loud” in Italian. In the 1730s the German builder Gottfried Silbermann showed Bach one of his early pianos. Bach found the high notes too weak. In 1747, at the Potsdam court of Frederick the Great, he improvised on an improved model, and he later helped to sell Silbermann's pianos.


