The Tenor Banjo

"The tenor banjo is typically played with a plectrum. It became a popular instrument after about 1910. Early models used for melodic picking typically had 17 frets on the neck and a scale length of 19½ to 21½ inches. By the mid-1920s, when the instrument was used primarily for strummed chordal accompaniment, 19-fret necks with a scale length of 21¾ to 23 inches became standard. The usual tuning is cgd'a', like a viola or mandola, but some players (particularly in Irish traditional music) tune it Gdae′ like an octave mandolin, which lets the banjoist duplicate fiddle and mandolin fingering. The invention and/or popularisation of this tuning is usually attributed to Barney McKenna, banjoist with The Dubliners.

The tenor banjo was a common rhythm instrument in early 20th-century dance bands. Its volume and timbre suited early jazz (and jazz-influenced popular music styles) and could both compete with other instruments (such as brass instruments and saxophones) and be heard clearly on acoustic recordings. George Gershwin's Rhapsody in Blue, in Ferde Grofe's original jazz orchestra arrangement, includes tenor banjo, with widely-spaced chords not easily playable on plectrum banjo in its conventional tuning(s). With development of the archtop and electric guitar, the tenor banjo largely disappeared from jazz and popular music, though keeping its place in traditional "Dixieland" jazz."

-wikipedia