What keyboard instrument with bowed strings did Leonardo da Vinci design around 1488?

Leonardo da Vinci designed the viola organista around 1488 as a keyboard instrument with bowed strings.

The design combined a keyboard with a rotating wheel or wheels that rubbed against strings, producing sound in a way related to bowed string instruments. Pressing keys selected the strings, while the moving wheel supplied continuous friction.

Unlike a conventional organ, the viola organista was not primarily an air-powered instrument. It was also different from a harpsichord, whose strings are plucked, and a clavichord, whose strings are struck. Leonardo’s surviving drawings show the concept rather than a known finished instrument built by him.

Several modern makers have reconstructed versions from his notebooks. The instrument is therefore important both as a musical experiment and as evidence of Leonardo’s interest in combining mechanical systems with artistic technology.