The sound-producing elements of the organ, which distinguish it from all other musical instruments. Each pipe produces a single tone, and it takes a series of them, one per key, to play the entire gamut of the keyboard. Such a series is called a Rank, because the pipes are usually arranged in a row for mechanical reasons. Pipes are of two classes: flue pipes, with no moving parts except the air, like a whistle; and reed pipes, which have a vibrating tongue producing the tone and a resonator to modify its quality.
Organ pipes fall into one of four broad sound categories: principal, flute, string, and reed. The first three types are known as "flue" pipes and work like whistles. The majority of organ pipes are flue pipes. In contrast to the whistle-like flue pipes, the reed pipes work like clarinets or saxophones, but have a brass "tongue" instead of a cane reed. Some of the reed pipes are the loudest pipes in the organ.
The source of musical sound on an organ. Pipes may be made of wood or metal, and they may be open or stopped with caps. Their pitch depends on their length and nature, and their tone depends on their shape and the material from which they are made. Each pipe produces a single tone and is linked to a note on a keyboard or pedalboard.