The Barker lever is a pneumatic system which multiplies the force of a finger on the key of a tracker pipe organ.
This lever allowed for the development of larger, more powerful organs still responsive to the human hand.
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.