A Dictionary of Music and Musicians/Pneumatic Action
PNEUMATIC ACTION. A contrivance for lessening the resistance of the keys, and other moveable parts of an organ, previously attempted by others, and brought into a practical shape by Charles S. Barker between 1832 and 41, in which latter year it was first applied by Cavaillé-Coll to the organ of S. Denis. The necessity of some such contrivance may be realised from the fact that in some of the organs on the old system, a pressure of several pounds was required to force down each key. In Willis's Organ at the Alexandra Palace, London, if there were no pneumatic levers, the resistance to the finger at middle C with the couplers drawn would be 25 lbs. For a description of the invention see Organ, vol. ii. p. 599.
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