Viola organista

The viola organista is a musical instrument designed by Leonardo da Vinci. It uses a friction belt to vibrate individual strings (similar to how a violin produces sounds), with the strings selected by pressing keys on a keyboard (similar to an organ). 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.

Leonardo designed many different and elaborate models of viola organista, as preserved in his notebooks of 1488–1489 and in the drawings in the Codex Atlanticus and Manuscript H.

In the first model the friction of the strings was achieved by a mechanical bow traveling sideways. The second model featured a single rotating wheel, similar to that of the earlier hurdy-gurdy, to play strings. It differs in that a hurdy-gurdy has a small number of strings that are constantly in contact with the wheel, rather than a larger number of strings that can be lowered onto the wheel. A hurdy-gurdy has a keybox with tangents that change the pitches of the strings, rather like placing fingers on violin strings. Leonardo's innovation of a keyboard with a lowering mechanism allowed individual notes to be played, alone or in specific desired chords over a large range of pitches.

Both the mechanical bow and the rotating wheel concepts were abandoned in favor of a third and final model. The main idea of this design was to use one or more wheels, continuously rotating, each of which pulled a looping bow, rather like a fanbelt in an automobile engine, and perpendicular to the instrument's strings. The strings would be pushed downward into the bow by the action of the keys, causing the moving bow to sound the pitch of the string. In one design, the strings were fretted with tangents, so that there were more keys than strings (multiple notes, for example C and C#, would be played on one string). In another design, each note had its own string.

Leonardo's design shows a boxy, vaguely harpsichord-shaped instrument with a hand-cranked bow-wheel, and indeterminate number of strings or keys.

The first known instrument actually constructed using Leonardo's concept, is Hans Heyden's Geigenwerk of 1575. While the concept is the same, the design is very different; modern versions of the instrument have been more or less based on Heyden's design. An etching of the Geigenwerk from 1620 shows an instrument of about the stature and shape of a harpsichord (i.e., an piano-shape with flat sides and hard angles). The fully chromatic keyboard appears to have 44 keys, extending about three-and-a-half octaves from low E to a high B. (see illustration) This keyboard range is consistent with harpsichords of the day, although harpsichord keyboards more typically started on low C or low F. The number of strings can't be directly determined, but the design implies one string per key, or 44 strings.

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