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Acoustic guitar ()
A guitar is a stringed musical instrument played with the fingers or a plectrum (guitar pick).

The guitar is descended from the lute, and like the lute has frets on the fingerboard, to fix the positions of the notes, or scale. Guitars usually have six strings, although there are variations on this, the most common being a twelve-string guitar, the ukelele, which has four strings, and the bass guitar, which usually has four strings but also exists in five and six-string versions.

A variety of different tunings are used. The most common by far, known as "standard tuning", is (low to high) E-A-d-g-b-e'. Standard tuning has evolved to provide a good compromise of both simple fingering for many chords, and the ability to play common scales with minimal left hand movement.

Some common alternate tunings

  1. E-A-d-f#-b-e which provides the same intervals as for a renaissance lute and so you can play with your guitar directly from tablature.
  2. D-G-d-g-b-d commonly used for blues or slide guitar
  3. D-A-d-g-b-e' frequently used in folk music, and by nu metal bands

There are also tenor guitars, baritone guitars tuned ADGCEA (or GDGCDG, GDGCEA, GCGCEG, ...) a fifth lower than a normal guitar, treble guitars tuned a fourth higher than a standard (prime) guitar, and contrabass guitars, which are tuned one octave lower than prime guitars.

Broadly speaking, guitars can be divided into 2 categories:

  1. Acoustic guitars: The traditional guitar is not dependent on any external device for amplification, unlike the electric guitar (see below). However, the unamplified guitar is not a loud instrument, that is, it cannot "compete" with other instruments commonly found in bands and orchestras, in terms of sheer audible volume. Most acoustic guitars are available today with built in electronics to enable amplification. There are several subcategories within the acoustic guitar group: classical and flamenco guitars, both of which use nylon and composite strings, and steel string guitars, which includes the flat top, or "folk" guitar, the closely related twelve string guitar, and the arch top guitar. A recent arrival in the acoustic guitar group is the acoustic bass guitar, similar in tuning to the electric bass.
    1. Classical guitars: These are typically strung with nylon or gut, and amplification is provided by the resonant hollow body. They are normally played in a seated position and used to play classical music. Flamenco guitars are almost equal in construction, have a sharper sound, and are used in flamenco. In Mexico, the popular mariachi band includes a range of guitars, from the tiny requinto to the guitarron, a guitar larger than a cello, which is tuned in the bass register.
    2. Flat top guitars: Similar to the Classical guitar, but with a narrower, reinforced neck and stronger structural design, to sustain the extra tension of steel strings which produce a louder and brighter tone, the acoustic guitar is a staple in folk, traditional and blues music.
    3. Resonator, resophonic or dobro guitars: Similar to the flat top guitar, but with a metal resonator mounted in the middle of the top rather than an open sound hole. The purpose of the resonator is to amplify the sound of the guitar; this purpose has been largely superseded by electrical amplification, but the resonator is still played by those desiring its distinctive sound. This type of guitar is more commonly played face up, on the lap of the seated player, and often with a metal or glass slide.
    4. 12 string guitars usually have steel strings and are widely used in folk music and rock and roll. Rather than having only six strings, the 12-string guitar has pairs, like a mandolin. Each pair of strings is tuned either in unison (the two highest) or an octave apart (the others). They are made both in acoustic and electric forms.
    5. Archtop guitars are steel string, acoustic instruments which feature a violin-inspired design in which the top and back of the instrument are carved in a curved rather than a flat shape. Lloyd Loar of the Gibson company invented this variation of guitar after designing a style of mandolin of the same type. They were immediately adopted by both jazz and country musicians, but fell out of style when rock and roll grew popular since their design is not capable of extreme amplification.
    6. Acoustic bass guitars also have steel strings, and match the tuning of the electric bass, which is likewise similar to the traditional double bass viol, the "big bass", a staple of string orchestras and bluegrass bands alike.
  2. Electric guitars: Electric guitars can have solid, semi-hollow or hollow bodies, and produce little or very low sound without amplification. Electromagnetic pickups convert the vibration of the steel strings into electric signals which are fed to an amplifier through a cable or radio device. The sound is frequently modified by other electronic devices or natural distortion of valves in the amplifier. The electric guitar is used extensively in blues and rock and roll, and was commercialized by Gibson together with Les Paul and independently by Leo Fender. The electric bass is similar in tuning to the traditional double bass viol.
Hybrids of acoustic and electric guitars are also common. There are also more exotic varieties, such as double-necked guitars, all manner of alternate string arrangements, fretless fingerboards, and such.

See also: guitarist, bass guitar, Jazz guitar, electric guitar, Chitarrone, Casio guitar, Air guitar