A twelve-string guitar (or 12-string guitar) is a steel-string guitar with 12 strings in six courses, which produces a thicker, more ringing tone than a standard six-string guitar. Typically, the strings of the lower four courses are tuned in octaves, with those of the upper two courses tuned in unison. The gap between the strings within each dual-string course is narrow, and the strings of each course are fretted and plucked as a single unit. The neck is wider, to accommodate the extra strings, and is similar to the width of a classical guitar neck. The sound, particularly on acoustic instruments, is fuller and more harmonically resonant than six-string instruments. The 12-string guitar can be played like a 6-string guitar as players still use the same notes, chords and guitar techniques like a standard 6-string guitar, but advanced techniques can be challenging as players need to play or pluck two strings simultaneously.
Structurally, 12-string guitars, especially those built before 1970, differ from six-string guitars in the following ways:
Twelve-string guitars are made in both acoustic and electric forms. However, the acoustic type is more common.