Leonardo da Vinci designed the viola organista, a keyboard instrument intended to produce bowed-string sounds.
The player would press keys, while a mechanism brought rotating, resin-coated wheels or bows into contact with strings. This combined the control system of a keyboard with the sustained sound associated with bowed instruments such as violas.
Leonardo drew several versions of the idea in his notebooks during the late fifteenth and early sixteenth centuries. No surviving original instrument proves that he completed a playable model, but modern builders have constructed working interpretations from his drawings.
The viola organista is not simply a renamed organ or harpsichord. Unlike a harpsichord, which plucks strings, its defining concept is continuous friction from rotating elements. It also differs from a conventional viola because the performer controls pitch through keys rather than fingering a neck.