An octave twelve is a type of 12-string guitar fitted with a short-scale neck and a small solid body. It is tuned one octave higher than a standard guitar, giving it the tonal range of a mandolin, and enabling a guitarist to achieve a mandolin sound without learning mandolin fingering. The effect is similar to that of capoing a standard 12-string guitar at its twelfth fret. However, unlike a standard 12-string guitar, the courses of strings tuned in unison, rather than in octaves.
The octave twelve was invented by engineers at Vox, which sold the octave twelve as the "Mando-guitar" from 1964 to 1968. Notable users of the Mando-guitar include Brian Jones of The Rolling Stones, and George Harrison of The Beatles, who used it prominently on the song "Words of Love." Most modern octave twelves are modeled after the distinctive body shape of the Vox Mando-guitar.