Leonardo da Vinci invented the viola organista, a keyboard instrument that used continuously moving bowed strings.
Leonardo drew several versions of the instrument in his notebooks. Pressing keys selected strings, while a wheel or series of wheels rubbed against them to produce sustained tones. The concept combined the expressive sound of bowed string instruments with the organized pitch control of a keyboard.
The viola organista was not a standard organ and did not use pipes to create its sound. It also differed from a piano, whose hammers strike strings only when keys are pressed. Leonardo's design belongs to a long history of experimental keyboard instruments that sought to imitate orchestral or vocal effects.
No surviving Renaissance example proves that Leonardo completed the instrument. Modern builders have made working reconstructions based on his drawings, allowing listeners to hear the principle that his sketches described.