Leonardo da Vinci designed the viola organista, a keyboard instrument with bowed strings.
The instrument combined a keyboard with a rotating wheel or belt mechanism. Pressing a key would bring a string into contact with the moving surface, producing a sustained sound in a way related to bowed string instruments. Leonardo explored versions of the idea in notebooks from the late 15th and early 16th centuries.
Unlike a harpsichord, which plucks strings, or a piano, which strikes them, the viola organista was intended to create sound through continuous friction. Leonardo's drawings show several arrangements, but he did not leave a surviving original instrument that can be identified with certainty.
The design illustrates his interest in linking music, mechanics, and materials. Modern makers have built playable reconstructions, but these are interpretations of the sketches rather than authenticated Renaissance instruments. The name “viola organista” is modern and describes the instrument's combination of viola-like sound production and organ-like keyboard control.