Guitar

The guitar is a stringed musical instrument. It is generally played with the fingers of the left hand{{ref|rhlh}}. The right hand plucks the strings with either the fingers or a plectrum, (guitar pick). The sound is produced by vibrating strings, which in turn resonate the body and neck.

Acoustic and electric guitar

Broadly speaking, guitars can be divided into 2 categories:

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• Acoustic guitars: Unlike the electric guitar, the traditional guitar is not dependent on any external device for amplification. The shape and resonance of the guitar itself creates acoustic amplification. 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. Many 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.
• Renaissance and Baroque guitars: These are the gracile ancestors of the modern classical guitar. They are substantially smaller and more delicate than the classical guitar, and generate a much quieter sound. The strings are paired in courses as in a modern 12 string guitar, but they only have four or five courses of strings rather than six. They were more often used as rhythm instruments in ensembles than as solo instruments, and can often be seen in that role in early music performances. (Gaspar Sanz' Instrucción de Música sobre la Guitarra Española of 1674 constitutes the majority of the surviving solo corpus for the era.) Renaissance and Baroque guitars are easily distinguished because the Renaissance guitar is very plain and the Baroque guitar is very ornate, with inlays all over the neck and body, and a paper-cutout inverted "wedding cake" inside the hole.
• Classical guitars: These are typically strung with nylon strings. Amplification is provided by the resonant hollow body, and the vibration of the thin, pliant top. In all acoustic guitars, the strings, though vibrating with sufficient energy to produce a strong sound, can not do so by themselves because they are too small and thin: air merely slips around them rather than being projected outward. The joining of the strings to a large membrane, the top, which they pull back and forth where they connect to it at the bridge, creates an effective air-moving system because the top is large enough that the air can not readily side step its motion. Sound only travels at 330 meters per second -- somewhat quickly, perhaps -- but if we recall that a guitar string typically switches from backward motion to forward motion every 1/600th of a second, we see that the air only has a chance to go about 1/2 meter, and the approximately 1/2 meter dimensions of a guitar top are enough to thwart its attempted evasive rush.
  These guitars 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. The father of the modern classical guitar was Antonio Torres Jurado.
• Flat top guitars: Similar to the classical guitar, however the body size is usually significantly larger than a classical guitar and it has 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, Old-time music and blues music.
• Resonator, resophonic or Dobro^® guitars: Similar to the flat top guitar in appearance, but with sound produced by a metal resonator mounted in the middle of the top rather than an open sound hole, so that the physical principle of the guitar is actually more similar to the banjo. 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. The type of resonator guitar with a neck with a square cross-section -- called "square neck" -- is usually played face up, on the lap of the seated player, and often with a metal or glass slide. The round neck resonator guitars are normally played in the same fashion as other guitars, although slides are also often used, especially in blues.
• 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.
• Archtop guitars are steel string, instruments which feature a violin-inspired f-hole design in which the top (and often the back) of the instrument are carved in a curved rather than a flat shape. Lloyd Loar of the Gibson Guitar Corporation invented this variation of guitar after designing a style of mandolin of the same type. The typical Archtop is a hollow body guitar whose form is much like that of a mandolin or violin family instrument and may be acoustic or electric. Some solid body electric guitars are also considered archtop guitars although usually 'Archtop guitar' refers to the hollow body form. Archtop guitars were immediately adopted upon their release by both jazz and country musicians and have remained particularly popular in jazz music, usually using thicker strings (higher guaged round wound and flat wound) than acoustic guitars. Archtops are often louder than a typical dreadnought acoustic guitar. The electric hollow body archtop guitar has a distinct sound among electric guitars and is consequently appropriate for many styles of rock and roll. Many electric archtop guitars intended for use in rock and roll even have a Tremolo Arm.
• 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.
• Harp Guitars. Harp Guitars are difficult to classify as there are many variations within this type of guitar. They are typically rare and uncommon in the popular music scene. Most consist of a regular guitar, plus additional 'harp' strings strung above the six normal strings. They guitar itself is usually acoustic and the harp strings are usually tuned to lower notes than the guitars tuning, for an added bass range. They will also not have a fingerboard or frets behind the harp strings. Some harp guitars also feature much higher pitch strings strung below the traditional guitar strings. The number of harp strings varies greatly, depending on the type of guitar and also the players personal preference, seeing as they are often custom made.
• Electric guitars: Electric guitars can have solid, semi-hollow or hollow bodies, and produce little or very low sound without amplification. Electromagnetic pickups (single and double coil) 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 (vacuum tubes) 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 lower fretboard action (the height of the strings from the fingerboard) and its electrical amplification lend the electric guitar to some techniques which are harder (or impossible) to execute on acoustic guitars. These techniques include tapping, extensive use of legato through pull-offs and hammer-ons (a.k.a. slurs in the traditional Classical genre), pinch harmonics, volume swells and use of a Tremolo arm or effects pedals.
• 7 string guitars were developed in the 1990s (earlier in jazz) to achieve a much darker sound through extending the lower end of the guitar's range. Used by bands such as Ko?n and players such as Steve Vai. Meshuggah & Charlie Hunter go a step further, using an 8 string guitar with two extra low strings.

The electric bass is similar in tuning to the traditional double bass viol.

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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 (used almost exclusively on bass guitars, meant to emulate the sound of a stand-up bass), and such.

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