Which Leonardo da Vinci invention used a rotating drum to create a continuous bowed sound?

Leonardo da Vinci’s viola organista used a rotating drum or wheel to create a continuous bowed sound.

The instrument was one of Leonardo’s attempts to combine keyboard control with the sustained tone of bowed strings. Pressing keys selected strings, while a rotating mechanism rubbed them continuously, producing sound without a separate bow moved by a musician.

Leonardo drew several related versions rather than leaving one fully standardized final model. This is why modern reconstructions differ in details such as the shape of the bowing wheel, the number of strings, and the arrangement of the keyboard.

The viola organista is sometimes confused with a hurdy-gurdy, which also uses a rotating wheel to sound strings. The key distinction is that Leonardo’s design was keyboard-operated, making it closer to a mechanically bowed keyboard instrument.