Katzenklavier: a piano keyboard with keys pulling the tails on a row of cats arranged by meow pitch.
The existing drawings, based on historical descriptions of the Katzenklavier, suggested that the instrument consisted of a keyboard, with seven to nine cats held in cages corresponding to the approximate pitch of their mewling.
Each of the cats' tails is stretched out and held down. Above each tail is a nail. Depressing a key assigned to a specific cat causes a mechanism to drive the nail into the tail resulting in a shriek from the poor animal.
Apparently, the contraption was never built. It was invented sometime in the 17th century by Athanasius Kircher, a German Jesuit renaissance man operating in the fields of medicine, oriental studies and geology.
The instrument was described by German physician Johann Christian Reil (1759–1813) for the purpose of treating patients who had lost the ability to focus their attention. Reil believed that if they were forced to see and listen to this instrument, it would inevitably capture their attention and they would be cured.