The name Stopped Diapason is the traditional English equivalent of the German Gedeckt, the French Bourdon, and the Spanish Tapadillo. It dates at least as far back as the beginning of the 16th century, and was adopted by early American organ builders. The name denotes a stopped flute of 8' pitch, usually made of wood, though sometimes of metal from middle C upward. Bonavia-Hunt suggests that its stoppers are sometimes pierced after the manner of a Chimney Flute. Sumner describes the Stopped Diapason as the second 8' stop in English Great, Choir and Swell organs until the smaller-scaled Lieblich Gedeckt became popular after 1851, but notes that it �did not cloy as quickly as modern lieblichs�. According to Wedgwood, early English builders frequently voiced this stop with a prominent 12th, thus having excellent blending properties: they were virtually Quintatons. Hopkins & Rimbault describe its tone as fluty and mellow, free from all reediness or roughness, and mention that when used alone, it is better suited for solo work than polyphony.
Osiris contains about 300 examples of Stopped Diapason, about 250 examples of Violon (not all of which are stopped flutes), about 75 examples of Stopped Flute, 10 examples of lûte Bouchée (all from the 20th century). No examples are known of Flauto Coperto (mentioned only by Williams).