What musical instrument did Leonardo da Vinci redesign with a keyboard and rotating wheel?

Leonardo da Vinci redesigned a keyboard instrument with a rotating wheel, known today as the viola organista. Pressing keys selected strings while a continuously turning, rosined wheel rubbed them, producing sustained bowed tones.

Leonardo drew several versions of the instrument in manuscripts from the late 15th and early 16th centuries. It combined the controllable pitches of a keyboard with the continuous sound of bowed strings. The idea addressed a musical problem: keyboard players normally cannot sustain notes in the manner of violinists.

No authenticated Leonardo-built viola organista survives. Modern makers have constructed playable versions from his drawings, though they differ in details. The instrument should not be confused with a conventional organ, harpsichord or viola da gamba; it is a hybrid keyboard-and-string machine.