These pages comprise a dictionary of terms relating to the pipe organ. Please keep definitions to a few sentences, and do not include pictures or sound clips. When more space is needed for a term, a new page can be created for it. Machine Stop Magnet Mandrel [noun] - a wooden or metal cylinder or cone used for forming pipe metal into shape for making organ pipes. Manometer [noun] a device for measuring wind pressure, consisting of a U-shaped tube partly full of water. The wind pressure is measured by the displacement of the water by the wind, and expressed in inches or millimeters. Melodion Motor