A cat organ or cat piano (German: Katzenorgel or Katzenklavier, French: orgue à chats or piano à chats/piano chats) is a hypothetical musical instrument which consists of a line of cats fixed in place with their tails stretched out underneath a keyboard so that they cry out when a key is pressed. The cats would be arranged according to the natural tone of their voices.
There is no official record of a cat organ actually being built; rather it is described in literature as a bizarre concept. "The details of the cat organ present it clearly as an instrument cat lovers might wish was a fictional horror." The instrument is used in stories which criticize the cruelty of royalty while the piganino, a similar instrument using pigs, has been used to criticize the poor.
This instrument was described by the French writer Jean-Baptiste Weckerlin in his book Musiciana, extraits d’ouvrages rare ou bizarre (Musiciana, descriptions of rare or bizarre inventions):
When the King of Spain Felipe II was in Brussels in 1549 visiting his father the Emperor Charles V, each saw the other rejoicing at the sight of a completely singular procession. At the head marched an enormous bull whose horns were burning, between which there was also a small devil. Behind the bull a young boy sewn into a bear skin rode on a horse whose ears and tail were cut off. Then came the archangel Saint Michael in bright clothing, and carrying a balance in his hand.
The most curious was on a chariot that carried the most singular music that can be imagined. It held a bear that played the organ; instead of pipes, there were sixteen cat heads each with its body confined; the tails were sticking out and were held to be played as the strings on a piano, if a key was pressed on the keyboard, the corresponding tail would be pulled hard, and it would produce each time a lamentable meow. The historian Juan Christoval Calvete, noted the cats were arranged properly to produce a succession of notes from the octave... (chromatically, I think).