The mandolin-banjo is a hybrid instrument, combining a banjo body with the neck and tuning of a mandolin or violin (depending on whether fretted or not and how many strings it has). It is a soprano banjo. It has been independently invented in more than one country, being called banjolin and banjourine in English speaking countries,banjoline and bandoline in France, and the Cümbüş in Turkey.
The instrument has the same scale length as a mandolin (about 14 inches); with 4 courses of strings tuned identically to the violin and mandolin (low to high: GDAE). The movable bridge stands on a resonant banjo-like head typically 10 inches in diameter and currently usually made of plastic. Originally heads were made of skin and varied in diameter to as small as five inches. Larger heads were favored, however, as they were louder, and thus more audible in band settings.
Inventors were experimenting to create amplified instruments in the days before electric amplification. The first patent for a mandolin-banjo was taken out in 1882 by Benjamin Bradbury of Brooklyn. The name banjolin was first patented by John Farris in 1885. The instrument was popularized prior to the 1920s, when the tenor banjo became more popular. In the heyday of mandolin orchestras and banjo bands (late 19th–early 20th century), all sorts of instruments were produced. The mandolin-banjo is one of the hybrids that resulted. It enabled mandolinists to produce a banjo sound without having to learn that instrument's fingerings. The instrument adds the banjo's volume to the mandolin.
The banjolin is different from the banjo-mandolin in the number of strings that it has. Banjolins today are supposed to have four strings instead of 8 strings (in courses or pairs). However, that distinction is not universal; the banjolin name was patented in 1885 by John Farris for an instrument with 8 strings. The Farris banjolin was offered in soprano, alto, tenor, and bass models. However, he "converted it to a four-string instrument," maintaining the mandolin and violin scale length and tuning (GDAE).