"a little girl in a smock cranked a barrel organ"
American organ grinder with barrel organ and performing monkey (1892)
Public DomainAmerican organ grinder with barrel organ and performing monkey (1892) - Credit: Library of Congress

A barrel organ is a mechanical musical instrument consisting of bellows and one or more ranks of pipes housed in a case, which is operated by a person turning a crank.

The barrel organ was the traditional instrument of the organ grinder, a type of street performer which existed in great numbers at the end of the 19th century and the beginning of the 20th century.