Tibia Clausa
A Tibia Clausa is a type of pipe organ pipe. It is a large-scale, stopped wood flute pipe, usually with a leathered lip. The rank was invented by Robert Hope-Jones. Tibia Clausas provides the basic foundation tone of the organ with few overtones or harmonics. The Tibia Clausa is arguably the most important rank of pipes in a theatre pipe organ, with some organs having as many as 5. The stop shares similarities with the Bourdon and the Gedackt found in some church pipe organs. In the 18th and 19th centuries, Tibia Clausa was sometimes used as an alternate name for Doppelflöte. Most tibias are made from wood, as by Wurlitzer etc., although examples of metal tibias may be found made by the John Compton Organ Company. The Tibia Clausa, or Tibia, is generally found at , , , and  pitches as a unified rank. The mutation ranks Tibia Quint , Twelfth  and Tierce  are also drawn from this unified rank of 97 pipes. In some larger organs, a second Tibia rank may be present, extended to  instead of , allowing a  Nineteenth mutation and a  Piccolo to be drawn from this rank. A few of the largest theatre organs, and some church organs, may have a separate  Tibia Clausa rank of 12 pipes. In smaller organs, a Bourdon or Stopped Diapason may be substituted for a Tibia Clausa at  pitch. The Tibia may be voiced on wind pressures from  . The Tibia is often used as a chorus stop (several footages played simultaneously, such as 16, 8, 4, and 2 ft, usually with tremulant; although it is also used as a solo stop in quieter or more reflective musical passages. Other variants of the Tibia include:  Tibia Bass, Tibia Flute, Tibia Major, Tibia Minor, Tibia Plena (open tibia) and Tibia Rex. References

Further reading

External links 
 Encyclopedia of Organ Stops: Tibia Clausa
 The Cinema Organ Society: Tibia

Flute type organ stops