Various, Encyclopaedia Britannica, 11th Edition…
“ In order to increase the compass and musical possibilities of the bugle, two methods have been adopted, the use of (1) keys and (2) valves. The application of keys to the bugle produced the Kent bugle, and later the ophicleide. The application of valves produced the family of saxhorns. The use of keys for wood wind instruments was known early in the 15th century, [3] perhaps before. In 1438, the duke of Burgundy paid Hennequin Haulx, instrument-maker of Brussels, 4 ridres a piece for three tenor bombards with keys. ”
