The twelve string guitar is an acoustic or electric guitar with twelve strings, which produces a richer, more ringing tone than a standard six string guitar. Essentially, it is a type of guitar with a natural chorus effect due to the subtle differences in the frequencies produced by either of the two strings on each course.
The strings are placed in courses of two strings each that are usually played together. The two strings in each bass course are normally tuned an octave apart, while each pair of strings in the treble courses is tuned in unison. The tuning of the second string in the third course (G) varies: some players use a unison string which is less prone to breakage, others prefer the distinctive high-pitched, bell-like quality an octave string makes in this position. Some players, either in search of distinctive tone or for ease of playing, will remove some of the doubled strings. For example, removing the higher octave from the three bass courses simplifies playing running bass lines, but keeps the extra treble strings for the full strums.
The tension placed on the instrument by the strings is great, and because of this, 12 string guitars have a reputation for warping after a few years of use. Some twelve-string guitars have non-traditional structural supports to prevent or postpone such a fate, at the expense of appearance and tone. Until recently, twelve-string guitars were nearly universally tuned lower than the traditional EADGBE, to reduce the stresses on the instrument. Lead Belly may have used a low C-tuning{See Julius Lester/Pete Seeger The 12-String Guitar as Played by Leadbelly, Oak Publications, New York, 1965, 6}}.
Some performers prefer the richness of an open tuning due to its near-orchestral sound. For a very complex plucked-string sound, the 12-string can be set to standard tuning (or possibly an octave lower), then the top one and low two string pairs can be tuned to whole-tone intervals. The usual gamut of guitar tunings are also available. Many performers who play the twelve-string guitar use an ordinary six-string guitar as their primary instrument, switching to the twelve-string guitar for certain songs that seem to call for a brighter sound.
Because it is substantially more difficult to pluck individual strings on the twelve-string guitar, and almost impossible to bend notes tunefully, the instrument is rarely used for lead musical parts. 12-string guitar is however primarily suited to a rhythm or accompaniment role and is often used in folk songs and some popular music. Some hard rock and progressive rock musicians use double-necked guitars, which have both six-string and twelve-string components, allowing the guitarist easy transition between different sounds.
The greater number of strings complicates playing, particularly for the plucking (or picking) hand. The gap between the dual-string courses is usually narrower than that between the single-string courses of a conventional six-string guitar, so more precision is required with pick or fingertip when not simply strumming chords. The pairing of thin, easily broken octave strings with larger, stiffer bass strings presents difficulties to the player also, and only a very skilled player can reliably pluck single strings from within a course at any speed (notably the very high octave G string, which is the highest-pitched string on the instrument). Nevertheless, with practice, the twelve-string guitar is not unduly difficult to play. It is, however, generally used in a fairly restricted role which emphasises its strengths: rich ringing, full-bodied chords, and fast, rippling single plucked notes on the twinned strings. Twelve-string guitars are made in both acoustic and electric form. However, it is the acoustic type that is most common.
Performers who use acoustic 12-string guitars span a range of genres, from folk (Arlo Guthrie) and traditional blues (Lead Belly) to folk rock (Paul Simon) (Neil Young) and rock bands (George Harrison of The Beatles and Pete Townshend of The Who)
Some musicians, notably Leo Kottke and John Butler, use it as their main instrument. Electric Rickenbacker 12-string users include a range of jangle pop guitarists, ranging from Jim/Roger McGuinn (The Byrds) to Peter Buck (R.E.M.). The Gibson EDS-1275 electric 12-string was used by blues rock/early heavy metal guitarist Jimmy Page (Led Zeppelin), Guns and Roses guitarist Slash, Alex Lifeson of Rush, Tom Morello of Rage Against the Machine, System Of A Down & Scars On Broadway guitarist Daron Malakian. For a longer list, see the List of 12-string guitar players article.