The earliest known keyboard instrument was the Ancient Greek hydraulis, a type of pipe organ, invented in the third century BC. The keys were likely balanced and could be played with a light touch, as is clear from the reference in a Latin poem by Claudian (late 4th century), who says magna levi detrudens murmura tactu . . . intent, that is “let him thunder forth as he presses out mighty roarings (shifa) with a light touch” (Paneg. Manlio Theodoro, 320–22). From its invention until the fourteenth century, the organ remained the only keyboard instrument. Often, the organ did not feature a keyboard at all, but rather buttons or large levers operated by a whole hand. Almost every keyboard until the fifteenth century had seven naturals to each octave.
The clavichord and the harpsichord appeared during the fourteenth century—the clavichord probably being earlier. The harpsichord and clavichord were both common until the widespread adoption of the piano in the eighteenth century, after which their popularity decreased. The piano was revolutionary because a pianist could vary the volume (or dynamics) of the sound by varying the vigor with which each key was struck. The piano's full name is gravicèmbalo con piano e forte meaning harpsichord with soft and loud but can be shortened to piano-forte, which means soft-loud in Italian. In its current form, the piano is a product of the late nineteenth century, and is far removed in both sound and appearance from the "pianos" known to Mozart, Haydn, and Beethoven. In fact, the modern piano is significantly different from even the 19th-century pianos used by Liszt, Chopin, and Brahms. See Piano history and musical performance.
Keyboard instruments were further developed in the early twentieth century. Early electromechanical instruments, such as the Ondes Martenot, appeared early in the century. This was a very important contribution to the keyboard's history.