Leonardo da Vinci’s viola organista was a keyboard instrument designed to create continuous bowed-string sound.
Unlike a normal keyboard, which strikes or plucks strings, the viola organista uses a rotating friction mechanism. Keys control which strings contact the moving wheels, belts, or bows, producing tones that resemble those of bowed instruments. The concept could allow one performer to play several notes while maintaining a sustained sound.
The instrument is named for its intended viola-like tone and its keyboard operation. It should not be confused with a hurdy-gurdy: a hurdy-gurdy normally uses a hand-turned wheel and a set of strings, while Leonardo’s design uses a keyboard to control the sounding strings.
Leonardo produced drawings rather than a surviving original instrument. Modern reconstructions have shown that the concept can work, though the exact mechanism varies because the notebooks contain multiple designs and do not provide a single complete manufacturing plan.