What instrument did Leonardo da Vinci design by combining a keyboard with a bowed wheel?

Leonardo da Vinci designed the viola organista by combining a keyboard with a bowed wheel.

The instrument was intended to produce sustained, string-like tones. Pressing keys selected strings, while a rotating wheel rubbed against them much as a bow does on a violin. Leonardo drew several versions, including designs recorded in the Codex Atlanticus and the Codex Madrid II.

Unlike a conventional organ, the viola organista was not primarily a pipe instrument. Unlike a harpsichord, it did not pluck strings. Leonardo’s drawings show a family of related mechanisms rather than one standardized instrument, and no surviving original instrument from his workshop is known. Modern makers have built playable reconstructions based on the sketches, allowing listeners to hear the principle Leonardo explored.