created using warm glass and stained glass techniques by Xaver Wilhelmy. Three Wilhelmy glass ranks exist in the United States, two in a private collection in West Virginia and one in a private collection in Virginia. The image at left shows the Wilhelmy American Flag Glass Pipe Organ that was created as a part of a Memorial Proposal for Ground Zero after the events of September 11, 2001. Shapes The bodies of organ pipes are generally made in three shapes: cylindrical, conical, or rectangular. Cylindrical pipes are simple cylinders, while conical pipes are in the shape of a tapering or expanding cone. Rectangular pipes form cuboid shapes with either a square or rectangular cross-section when viewed from above. There are some irregular shapes as well: the Flûte triangulaire, for example, has a triangular cross-section when viewed from above. In addition, a cylindrical or rectangular pipe can be tapered: that is, it can be made to be wider at the bottom than at the top. The internal shape of the pipe is a major factor in tone color. The end of the pipe opposite the reed or mouth may be either open or closed (also known as stopped). A closed flue pipe with a uniform cross-section sounds an octave lower than a similar open pipe of the same length. Also, such an open pipe produces a tone in which both the even-numbered and the odd-numbered partials are present, while a stopped pipe, such as a gedackt, produces a tone with odd-numbered partials. The tone of a stopped pipe tends to be gentler and sweeter than that of an open pipe, though this is largely at the discretion of the voicer. Certain organ pipes are also mounted horizontally in the shape of a trumpet horn so as to project the sound farther. These pipes are known as en chamades. However, when such a commanding tone is desired but it is impossible to mount an en chamade on the case, a hooded reed is used. This type of pipe stands vertically and has a 90-degree bend at the top which acts to project the sound outward in the same way an en chamade does, but can be placed in the interior of an organ. Pitch The pitch produced by an organ pipe is determined in two fundamentally different ways. For a reed pipe it is determined mainly by the mechanical properties of the