Twelve-string guitar
The interference between the out-of-phase vibrations produces a phenomenon known as a beat that results in a periodic rise and fall of intensity which is, in music, often considered pleasing to the ear.
[6] The 12-string guitar did not become a major part of blues and folk music till the 1920s and the 1930s, when their "larger than life"[5] sound made them ideal as solo accompaniment for vocalists, especially Lead Belly and Blind Willie McTell.
Initially, it was primarily used for accompaniment, owing to the greater difficulty of picking or executing string "bends" on its double-strung courses.
In the later 20th century, however, a number of players devoted themselves to producing solo performances on the 12-string guitar, including Leo Kottke, Peter Lang, John McLaughlin, Larry Coryell, Ralph Towner, Robbie Basho, Roger Whittaker, Jack Rose, and James Blackshaw.
The electric 12-string gained prominence with the introduction in 1964 of the Rickenbacker 360,[9] made famous through George Harrison's use of it on The Beatles' album A Hard Day's Night and many subsequent recordings.
[16] In 1965, inspired by Harrison, Roger McGuinn made the Rickenbacker 12-string central to The Byrds' folk rock sound, further popularising the instrument.
[20][21] However, from the 1970s, some progressive rock, hard rock, and jazz fusion guitarists, most notably Jimmy Page of Led Zeppelin, Don Felder of the Eagles, John McLaughlin of The Mahavishnu Orchestra and Alex Lifeson of Rush used double-necked guitars such as the Gibson EDS-1275, with six-string and 12-string necks, for live appearances, allowing easy transition between different sounds mid-song.
[22] The post punk era of the late '70s and early '80s saw a resurgence of electric 12-string guitar use among '60s-influenced alternative rock, pop, and indie guitarists.
The extra tension placed on the instrument by the doubled strings is high, and because of this additional stress on their necks and soundboards, 12-string guitars long had a reputation for warping after a few years of use.
Until the wide spread adoption by American makers of the truss rod after WWII, 12-string guitars were frequently tuned lower than the traditional EADGBE to reduce the stresses on the instrument.
[citation needed] To additionally reduce string tension, 12-string guitars built prior to 1970 typically had shorter necks and scale lengths than six-string guitars, which made frets more closely spaced, with some notable exceptions such as the instruments made by the Oscar Schmidt company before their bankruptcy, which usually had scale lengths of around 26.5".
Their bridges, especially in acoustic guitars, had a larger reinforcement plate for the same reason, and tailpiece and floating-bridge setups were far more common than on six string instruments as another way to combat the effect of the high tension.
Contemporary 12 string guitars are commonly built to the same dimensions and scale as their six-string counterparts, albeit still usually with heavier build and bracing.
Some performers have experimented with tuning the two strings within a course to intervals other than octaves or unisons: jazz guitarists such as Ralph Towner (of Oregon), Larry Coryell, and Philip Catherine have tuned the bass courses of their 12-string guitars to the upper fifths and trebles to the lower fourths instead of octaves and unisons;[31] Michael Gulezian tuned strings in the top two courses to whole-tone intervals (and possibly some of the other strings an octave lower) to achieve a very rich, complex sound.
[34] This configuration yields a resonant timbre reminiscent of the venerable bajo sexto, but adds significantly more tension on the bridge and neck.
Fretting chords requires greater force, and the width of the neck and the added string tension combine to make soloing and string-bending challenging.
