Harmonic instruments: bagpipe, organ and a mechanical viola
Bellows for continuous wind and a gear train that draws the bow
Under the heading 'Of harmonic instruments' Leonardo sketches three sounding machines: a bagpipe (piva) fed by two alternating bellows so the wind stays continuous, an organ of flattened pipes made of strips or paper, and a keyed viola whose bow is drawn back and forth by a gear train worked from the player's elbow. The drawings show a triangular bellows frame at upper right, a standing man holding an instrument, and, along the lower edge, the belt, ratchet and wheels that move the bow. Letter labels n, m, b, a and r, m, f, n key the mechanisms to the text. The mechanical reckoning ties elbow travel to bow travel through a ratchet and a larger wheel.
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Bagpipe with two alternating bellows for continuous wind
For the bagpipe the partition of the bellows a is fixed to the belt, while b is fixed to the arm; as the arm moves in and out it opens and closes the bellows as needed. When bellows n opens, bellows m closes, and when m opens, n closes, so that the wind is continuous.
Organ of flattened pipes
An organ of flattened pipes (canne stiacciate) is to be made of strips or of paper. The nearby figure marks the flattened pipes and the keys of the organ.
Keyed viola with a bow driven from the elbow
A bowed viola with keys (viola a tasti) is played by moving the little bow as one works a bellows with the elbows. The bow follows the right arm from key to key, so the sounding length diminishes together with the notes; the figures are labelled r, m, f, n and gomito (elbow).
Gear ratio linking elbow travel to bow travel
When the elbow moves two fingers, the toothing n also moves 2 fingers and makes the pinion m give one full turn. The larger wheel likewise turns once, equal to 1/3 of a braccio, so the mechanism draws back and releases a whole braccio of bow across the strings.