Which Leonardo da Vinci instrument combined a keyboard with a continuous bow?

Leonardo da Vinci’s viola organista combined a keyboard with a continuous bow. The keyboard selected strings, while a moving bow mechanism was intended to make them vibrate and produce sustained musical tones.

Leonardo’s sketches show several ways to arrange the strings and bowing surfaces. The idea offered a keyboard player access to the expressive quality associated with bowed instruments, rather than the brief pluck of a harpsichord or the air-driven sound of a pipe organ.

The viola organista was never established as a standard Renaissance instrument. Its name can cause confusion because it does not mean that the machine was a conventional organ. Modern reconstructions have demonstrated that the principle can work, although builders must interpret incomplete drawings and choose practical materials for the mechanisms Leonardo only sketched.