The Barker lever is a
pneumatic system which multiplies the force of a finger on the key of a
trackerpipe organ. It employs the wind pressure of the organ to inflate small
bellows called "pneumatics" to overcome the resistance of the pallets (
valves) in the organ's wind-chest. This
lever allowed for the development of larger, more powerful organs still responsive to the human hand. These larger organs first flourished in
France, e.g., the organ produced by
Cavaillé-Coll at
St. Sulpice. The first Barker lever was built in the
Cavaillé-Coll organ of the
Basilica of Saint-Denis.
This "contrivance" was named after
Charles Spackman Barker (1804-79), engineer and
organ-builder. A similar lever was developed by David Hamilton in 1835, and there has been debate whether Barker stole the design.
Bibliography
George Laing Miller: "The Recent Revolution in Organ Building", 1913, chapter III
David Bridgeman-Sutton:
"Barker-lever". This is based on the following two print sources, Hinton suggesting Barker's copying & Thistlethwaite noting the differences in design.
John William Hinton: The Story of the Electric Organ. London: Simpkin, Marshall, Hamilton, Kent & Co., 1909.
Nicholas Thistlethwaite: The Making of the Victorian Organ. Cambridge Musical Texts and Monographs. Cambridge: Cambridge University Press, 1990. Pp. 352–354.
P. Williams: "Organ." The New Grove Dictionary of Music & Musicians. (Stanley Sadie, ed.), vol. 13, New York: Macmillan, 1995, pp. 710–779.
Hans Dieter Meyer: Buchholz und Haupt, oder: Wie der Barkerhebel nach Deutschland kam. In: Ars organi 52 (2004). ISSN 0004-2919
Duncan Mathews, Charles Barker's Wondrous Machines. In: Organ builder 5 (2008), 17-20.