Banjo is a stringed musical instrument of African origin, popularised in the United States by slaves in the 19th century, then exported to Europe. It has a Tambourine like body with a hoop and a screw that secure the vellum belly to the frame. Screw stretchers are used to vary the tension of the belly. The strings pass over a violin-type, or pressure, bridge and are hitched to a tailpiece. In the 1890s, frets were added to the long neck, and a machine head with screws replaced the tuning pegs. The earliest banjos had four gut strings; later, from five to nine metal strings were used. The standard banjo has five metal strings. Four are tuned from the head, usually to C′–G′–B′–D″ upward from (notated) middle C. Preceding the C string is the chanterelle (drone, or thumb), a shorter string fastened to a screw midway in the banjo neck. It is tuned to the (notated) second G above middle C. The actual pitch is an octave lower than notated. Banjos played with a plectrum, or pick, rather than fingers lack the chanterelle. The banjo is widely played in the U.S. folk music and has also been used in Jazz ensemble.