The viola organista is a musical instrument designed by Leonardo da Vinci. It uses a friction belt to vibrate individual strings, with the strings selected by pressing keys on a keyboard. Leonardo's design has intrigued instrument makers for more than 400 years, but though similar instruments have been built, no extant instrument constructed directly from Leonardo's incomplete designs is known. Sometimes it is mistakenly referred to as the harpsichord viola, which is a different instrument.

The Codex Atlanticus is a 12-volume, bound set of drawings and writings by Leonardo da Vinci, the largest single set. Its name indicates the large paper used to preserve original Leonardo notebook pages, which was used for atlases. It comprises 1,119 leaves dating from 1478 to 1519, the contents covering a great variety of subjects, from flight to weaponry to musical instruments and from mathematics to botany. This codex was gathered in the late 16th century by the sculptor Pompeo Leoni, who dismembered some of Leonardo's notebooks in its formation. It is now in the Biblioteca Ambrosiana in Milan.