What Leonardo da Vinci musical invention used a keyboard to bow strings continuously?

Leonardo da Vinci’s keyboard string instrument was the viola organista.

Leonardo developed the idea in the 15th century and illustrated it in his notebooks. The instrument combined a keyboard with a mechanism that pressed strings against rotating wheels or a continuous bowing surface. Pressing keys selected the notes, while the moving mechanism produced sustained tones in a way that resembled a bowed string instrument.

The viola organista was an attempt to unite the control of a keyboard with the expressive sound of violas. Unlike a normal harpsichord, which plucks strings, the design was intended to bow them. Leonardo drew several related mechanisms, showing that he refined the concept rather than recording only one fixed model.

No securely documented original instrument built by Leonardo survives. Modern makers have constructed playable versions from the drawings, but those reconstructions require interpretation because the notebooks do not provide every manufacturing detail. The name is sometimes mistaken for an ordinary viola; it refers to a keyboard-controlled instrument.