The guitar is a musical instrument with ancient roots that is used in a wide variety of musical styles. It typically has six strings, but four, seven, eight, ten, and twelve string guitars also exist.
Guitars are recognized as one of the primary instruments in blues, country, flamenco, rock music, and many forms of pop. There is also a solo classical instrument. Guitars may be played acoustically, where the tone is produced by vibration of the strings and modulated by the hollow body, or they may rely on an amplifier that can electronically manipulate tone. Such electric guitars were introduced in the 20th century and continue to have a profound influence on popular culture.
Traditionally guitars have usually been constructed of combinations of various woods and strung with animal gut, or more recently, with either nylon or steel strings. Guitars are made and repaired by luthiers.
Like the Fender precision bass and the double bass, it commonly has four strings, normally tuned to E-A-D-G, making it an octave below the lowest four strings of the 6-string guitar. Like the electric bass, 5+ string models have been produced although these are relatively much less common. The physics of sound production means it is very hard to produce a usable low B string and five string varieties may be strung E-A-D-G-C instead.
There are two main varieties. The majority of acoustic basses are fretted but a significant number are fretless instead. Semi-fretted versions are also occasionally seen.
Because it is virtually impossible for a strictly acoustic bass to be heard over other instruments, even acoustic guitars, many (but by no means all) acoustic basses are fitted with internal pickups, either magnetic or piezoelectric or both, so that they can optionally be used with an amplifier.
There are also semi-acoustic models fitted with pickups and intended to be always used with an amplifier. The box of these is principally designed to produce a distinctive tone when amplified, similarly to semi-acoustic electric guitars. Thin-body semi-acoustic basses such as the violin-shaped H÷fner made famous by the early Beatles and several Fender models are not normally regarded as acoustic basses at all, but rather as hollow-bodied electric basses. As with semi-acoustic electric guitars, the line between acoustic instruments fitted with pickups and electric instruments with tone-enhancing bodies is sometimes hard to draw.
Other manufacturers, not mentioned above, include Eston, Gibson, Maton, Prestige and Tacoma.
Traditional music of Mexico features several varieties of acoustic bass guitars.
The baja sexto, with six pairs of strings, resembles a twelve-string guitar tuned an octave lower. The heavy gauge strings generate a large string tension, yet the guitar is built relatively lightly. The baja sexto began to be used in Texas in the 1920s with the rise of "Tex-Mex" music, where it continues to be used to play the parts which would be played by the piano in traditional American popular music. A Mexican variation of the Baja Sexto is the Bajo Sexto. The tuning of these instruments is (Capital letters are an octave lower than small letters):
The guitarron (more accurately guitarrˇn) or chitarrone is a very large, deep-bodied Mexican 6-string acoustic bass guitar played in Mariachi bands. Although obviously similar to the guitar, it is not a derivative of that instrument, but was independently developed from the sixteenth-century Spanish Bajo de U˝a. It achieves audibility by its great size, and does not require electric amplification. The guitarron is fretless, the strings are heavy guage, and the action is high, so that quite a bit of left hand strength is required. The strings are plucked strongly, two strings an octave apart at a time, which is facilitated by the unusual tuning, A D G c e A. (Unlikely but true guitarron trivia: the guitarron is played by Roy Estrada on the Mothers of Invention album Freak Out!.)