Listed only by Williams, who says: The large open bass pipes placed apart from, and on either side of, the G.O. [Grand Orgue] in some of the larger 15th-cent. French organs. The number varied from two to ten, the size to 32' (24' FF), the distance from the main chest perhaps 15'. Wind was probably brought to the pipes by long conduits fom the chest. Trompes as a term may be derived from tromba (�horn, trumpet�) to signify open pipes; but it may have developed from the architectural use of the term trompe to signify the �pendentive� - such bass or (in some cases) drone pipes being planted upon pendentive-like supports on the church wall. The trump was a short, sharply conical instrument familiar from at least the early Middle Ages.