Soprano brass instrument historically used for hunting and military signaling. It developed from an 18th-century semicircular German hunting horn with widely expanding bore. In the 19th century the semicircle was reshaped into an oblong double loop. Natural bugles use only harmonics 2–6 (producing tones of the C triad) in their calls (Reveille, Taps, etc.). The keyed bugle, patented in 1810, has six sideholes and keys which give it a complete chromatic scale. In the 1820s valves were added to produce the flügelhorn and, in lower ranges, the baritone, euphonium, and saxhorns.