Leonardo da Vinci designed the viola organista as a keyboard instrument whose strings were sounded by friction.
The unusual machine combined a keyboard with a set of strings and rotating wheels or belts. Pressing keys selected the strings, while the moving friction mechanism made them vibrate. In principle, this allowed one performer to control several bowed-string voices from a keyboard.
Leonardo drew several versions of the concept in his notebooks, but no complete original instrument is known to have survived. The design belongs to his continuing interest in joining musical performance with mechanical automation.
The viola organista is not simply a small organ and not a conventional harpsichord. A harpsichord plucks strings, whereas Leonardo’s concept used friction, giving it a closer mechanical relationship to instruments such as the viol and violin. Modern builders have created playable reconstructions from his drawings.