A classic guitar

The guitar is a musical instrument with ancient roots that adapts readily to a wide variety of musical styles. It typically has six strings, but four-, seven-, eight-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars also exist. The size and shape of the neck and the base of the guitar also vary, producing a variety of sounds. The three main types of guitars are the electric guitar, the classical guitar, and the acoustic guitar. Sometimes the last two are put in the same category.

Guitars are recognized as one of the primary instruments in flamenco, jazz, blues, country, mariachi, rock music, and many forms of pop. They can also be 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 1930s, and they have continued to have a profound influence on popular culture since then.

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. There are many brands of guitars, but some commonly known brands are Fender, Gibson, Dean, Gretsch, Ibanez, Martin, Jackson, Schecter, Taylor, Paul Reed Smith, B.C. Rich, ESP and Yamaha.

History

Before the development of the electric guitar and the use of synthetic materials, a guitar was defined as being an instrument having "a long, fretted neck, flat wooden soundboard, ribs, and a flat back, most often with incurved sides". The term is used to refer to a number of such related instruments that were developed and used across Europe in the modern era. Some types of guitars, which are themselves related to these European instruments, originated in the Americas.

The guitar, as usually defined, refers to a set of closely related stringed instruments created and used across Europe since the medieval period, making it a truly European instrument. The defining developments of the guitar occurred where it was especially popular during the modern era, in Latin Europe, namely Spain, Italy and France. Precursors of the guitar can be traced back as much as 4000 years to an Indo-European origin of stringed instruments once known in central Asia and India. For this reason guitars are distantly related to contemporary instruments from these regions, including the tanbur, setar and sitar, among others. The oldest known iconographic representation of an instrument displaying the essential features of a guitar is a 3,300 year old stone carving of a Hittite bard.

The modern word, guitar, was adopted into English from Spanish guitarra (German Gitarre, French Guitare), loaned from the medieval Andalusian Arabic qitara, itself derived from the Latin cithara, which in turn came from the earlier Greek word kithara, a descendant of Old Persian sihtar (Tar means string in Persian).

Illustration from a Carolingian Psalter from the 9th century, showing a guitar-like plucked instrument.

The guitar is descended from the Roman cithara brought by the Romans to Hispania around 40 AD, and further adapted and developed with the arrival of the four-string oud, brought by the Moors after their conquest of Iberia in the 8th century. Elsewhere in Europe, the indigenous six-string Scandinavian lut (lute), had gained in popularity in areas of Viking incursions across the continent. Often depicted in carvings c. 800 AD, the Norse hero Gunther (also known as Gunnar), played a lute with his toes as he lay dying in a snake-pit, in the legend of Siegfried. By 1200 AD, the four string "guitar" had evolved into two types: the guitarra morisca (Moorish guitar) which had a rounded back, wide fingerboard and several soundholes, and the guitarra latina (Latin guitar) which resembled the modern guitar with one soundhole and a narrower neck. In the 14th and 15th centuries the qualifiers "morisca" and "latina" were dropped and these four course instruments were simply called guitars.

The Spanish vihuela or "viola da mano", a guitar-like instrument of the 15th and 16th centuries, is often considered an important influence in the development of the modern guitar. It had lute- and viol-style tuning in fourths and a guitar-like body, although early representations reveal an instrument with a sharply-cut waist, very similar (or identical to) contemporary viols. It was also larger than the contemporary four course guitars. By the late 15th century some vihuelas began to be played with a fiddle leading to the development of the viol. By the sixteenth century the vihuela's construction had more common with the modern guitar with its curved one-piece ribs than with the viols, and more like a larger version of the contemporary four-course guitars. The vihuela enjoyed only a short period of popularity in Spain and Italy during an era dominated elsewhere in Europe by the lute; the last surviving published music for the instrument appeared in 1576. Meanwhile the five-course baroque guitar, documented in Spain in 1554, enjoyed popularity, especially in Italy, France and Spain from the late 16th century to the mid 18th century. Confusingly, in Portugal, the word vihuela referred to the guitar, whereas guitarra meant the "Portuguese guitar", a variety of cittern.

Types of guitars

The guitar player (c. 1672), by Johannes Vermeer

Guitars can be divided into two broad categories, acoustic and electric:

Acoustic guitars

An acoustic guitar is one not dependent on an external device to be heard but uses a soundboard which is a wooden piece mounted on the front of the guitar's body. The acoustic guitar is quieter than other instruments commonly found in bands and orchestras so when playing within such groups it is often externally amplified. Many acoustic guitars available today feature a variety of pickups which enable the player to amplify and modify the raw guitar sound.

There are several notable subcategories within the acoustic guitar group: classical and flamenco guitars; steel string guitars, which include the flat-topped, or "folk," guitar; twelve-string guitars; and the arched-top guitar. The acoustic guitar group also includes unamplified guitars designed to play in different registers, such as the acoustic bass guitar, which has a similar tuning to that of the electric bass guitar.

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 ivory or wood 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, played in a seated position and are used to play a diversity of musical styles including classical music. The classical guitar's wide, flat neck allows the musician to play scales, arpeggios and certain chord forms more easily and with less adjacent string interference than on other styles of guitar. Flamenco guitars are very similar in construction, but are associated with a more percussive tone. 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. In Colombia, the traditional quartet includes a range of instruments too, from the small bandola (sometimes known as the Deleuze-Guattari, for use when traveling or in confined rooms or spaces), to the slightly larger tiple, to the full sized classical guitar. The requinto also appears in other Latin-American countries as a complementary member of the guitar family, with its smaller size and scale, permitting more projection for the playing of single-lined melodies. Modern dimensions of the classical instrument were established by Antonio Torres Jurado (1817-1892). In recent years, the series of guitars used by the Niibori Guitar orchestra have gained some currency, namely:

• Sopranino guitar (an octave and a fifth higher than normal); sometimes known as the piccolo guitar
• Soprano guitar (an octave higher than normal)
• Alto guitar (a 5th higher than normal)
• Prime (ordinary classical) guitar
• Niibori bass guitar (a 4th lower than normal); Niibori simply calls this the "bass guitar", but this assigns a different meaning to the term than other parts of the community use, as his is only a 4th lower, and has 6 strings
• Contrabass guitar (an octave lower than normal)

The modern Ten-string guitar

The Modern/Yepes 10-string guitar (a classical guitar) adds four strings (resonators) tuned in such a way that they (along with the other three bass strings) can resonate in unison with any of the 12 chromatic notes that can occur on the higher strings; the idea behind this being an attempt at enhancing and balancing sonority.

Portuguese guitar

In spite of the name, it is not a guitar, but rather a cittern.

Flat-top (steel-string) guitars

Similar to the classical guitar, however, within the varied sizes of the steel-stringed guitar the body size is usually significantly larger than a classical guitar and it has a narrower, reinforced neck and stronger structural design. This allows the instrument to withstand the additional tension of steel strings. The steel strings produce a brighter tone, and according to many players, a louder sound. The acoustic guitar is used in many kinds of music including folk, country, bluegrass, pop, jazz and blues. Many variations are possible from the roughly classical-sized OO and Parlour to the large Dreadnought and Jumbo.

Archtop guitars

These are steel string instruments 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 Mandolin-Guitar Mfg. Co introduced the violin-inspired f-hole design now usually associated with archtop guitars, after designing a style of mandolin of the same type. The typical archtop guitar has a large, deep, hollow body whose form is much like that of a mandolin or violin family instrument. Nowadays, most archtops are equipped with magnetic pickups and are therefore both acoustic and electric. F-hole archtop guitars were immediately adopted upon their release by both jazz and country musicians and have remained particularly popular in jazz music, usually with flatwound strings.

Selmer-Maccaferri guitars

are usually played by those who follow the style of Django Reinhardt. It is an unusual-looking instrument, distinguished by a fairly large body with squarish bouts, and either a "D"-shaped or longitudinal oval soundhole. The strings are gathered at the tail like an archtop guitar, but the top is flatter. It also has a wide fingerboard and slotted head like a nylon-string guitar. The loud volume and penetrating tone make it suitable for single-note soloing and it is frequently employed as a lead instrument in gypsy swing.

An 8 string baritone tricone resonator guitar.

Resonator, resophonic or Dobro guitars

Similar to the flat top guitar in appearance, the sound of the resonator guitar is produced by a metal resonator mounted in the middle of the top. The physical principle of the guitar is therefore similar to the banjo. The original purpose of the resonator was to amplify the sound of the guitar. This purpose has been largely superseded by electrical amplification, but the resonator guitar is still played because of its distinctive sound. Resonator guitars may have either one resonator cone or three resonator cones. Three-cone resonators have two cones on the left above one another and one cone immediately to the right. The method of transmitting sound resonance to the cone is either a "biscuit" bridge, made of a small piece of hardwood, or a "spider" bridge, made of metal and larger in size. Three-cone resonators always use a specialized metal spider bridge. 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

The twelve string guitar usually has steel strings and is widely used in folk music, blues and rock and roll. Rather than having only six strings, the 12-string guitar has six courses made up of two strings each, like a mandolin or lute. The highest two courses are tuned in unison, while the others are tuned in octaves. The 12-string guitar is also made in electric forms.

Russian guitars

These are seven string acoustic guitars which were the norm for Russian guitarists throughout the 19th and well into the 20th centuries. The guitar is traditionally tuned to an open G major tuning.

Acoustic bass guitars

Have steel strings or gut strings and often the same tuning as an electric bass guitar.

Tenor guitars

A number of classical guitarists call the Niibori prime guitar a "Tenor Guitar" on the grounds that it sits in pitch between the alto and the bass. Elsewhere the name is taken for a 4-string guitar with a scale length of 23" (585 mm) – about the same as a Terz Guitar. The tenor guitar is tuned in fifths, C G D A, as is the tenor banjo and the cello. It is generally accepted that the tenor guitar was created to allow a tenor banjo player to follow the fashion as it evolved from Dixieland Jazz towards the more progressive Jazz that featured guitar. It allows a tenor banjo player to provide a guitar-based rhythm section with little to learn. A small minority of players (such as Nick Reynolds of the Kingston Trio) close tuned the instrument to D G B E to produce a deep instrument that could be played with the 4-note chord shapes found on the top 4 strings of the guitar or ukulele. The deep pitch warrants the wide-spaced chords that the banjo tuning permits, and the close tuned tenor does not have the same full, clear sound.

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. The instrument is usually acoustic and the harp strings are usually tuned to lower notes than the guitar strings, for an added bass range. Normally there is neither fingerboard nor 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 player's personal preference (as they have often been made to the player's specification). The Pikasso guitar; 4 necks, 2 sound holes, 42 strings] and also the Oracle Harp Sympitar; 24 strings (with 12 sympathetic strings protruding through the neck) are modern examples.

Extended-range guitars

For well over a century guitars featuring seven, eight, nine, ten or more strings have been used by a minority of guitarists as a means of increasing the range of pitch available to the player. Usually, it is bass strings that are added. Classical guitars with an extended range are useful for playing lute repertoire, some of which was written for lutes with more than six courses.

Guitar battente

The battente is smaller than a classical guitar, usually played with four or five metal strings. It is mainly used in Calabria (a region in southern Italy) to accompany the voice.

This Fender Stratocaster has features common to many electric guitars: multiple pickups, a whammy bar, volume and tone knobs.

Electric guitars

Electric guitars can have solid, semi-hollow, or hollow bodies, and produce little sound without amplification. Electromagnetic pickups convert the vibration of the steel strings into electrical signals, which are fed to an amplifier through a cable or radio transmitter. The sound is frequently modified by other electronic devices or the natural distortion of valves (vacuum tubes) in the amplifier. There are two main types of pickup, single and double coil (or humbucker), each of which can be passive or active. The electric guitar is used extensively in jazz, blues, and rock and roll, and was commercialized by Gibson in collaboration with Les Paul, and independently by Leo Fender of Fender Music. The lower fretboard action (the height of the strings from the fingerboard), lighter (thinner) strings, and its electrical amplification lend the electric guitar to some techniques which are less frequently used on acoustic guitars. These include tapping, extensive use of legato through pull-offs and hammer-ons (also known as slurs), pinch harmonics, volume swells, and use of a tremolo arm or effects pedals.

The first guitarist of note to use a seven string guitar was jazz guitarist George Van Eps, who was noted as a pioneer of this instrument. Solid body seven-strings were popularized in the 1980s and 1990s in part due to the release of the Ibanez Universe guitar, endorsed by Steve Vai. Other artists go a step further, by using an 8 string guitar with two extra low strings. Although the most common 7-string has a low B string, Roger McGuinn (of The Byrds and Rickenbacker) uses an octave G string paired with the regular G string as on a 12 string guitar, allowing him to incorporate chiming 12 string elements in standard 6 string playing. in 1982 Uli Jon Roth developed the "Sky Guitar", with a vastly extended amount of frets, which was the first guitar to venture into the upper registers of the violin. Roth's 7-string and 33 fret "Mighty Wing" guitar features an altogether 6-octave range.

The electric bass guitar 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 guitars with two, three, or rarely four necks, all manner of alternate string arrangements, fretless fingerboards (used almost exclusively on bass guitars, meant to emulate the sound of a stand-up bass), 5.1 surround guitar, and such.

Some electric guitar and electric bass guitar models feature Piezoelectric pickups, which function as transducers to provide a sound closer to that of an acoustic guitar with the flip of a switch or knob, rather than switching guitars.

Guitar construction and components

1. Headstock
2. Nut
3. Machine heads (or pegheads, tuning keys, tuning machines, tuners)
4. Frets
5. Truss rod
6. Inlays
7. Neck
8. Heel (acoustic) – Neckjoint (electric)
9. Body
10. Pickups
11. Electronics
12. Bridge
13. Pickguard
14. Back
15. Soundboard (top)
16. Body sides (ribs)
17. Sound hole, with Rosette inlay
18. Strings
19. Saddle
20. Fretboard (or Fingerboard)

General

Guitars can be constructed to meet the demands of both left and right-handed players. Traditionally the dominant hand is assigned the task of plucking or strumming the strings. For the majority of people this entails using the right hand. This is because musical expression (dynamics, tonal expression and colour etc) is largely determined by the plucking hand, while the fretting hand is assigned the lesser mechanical task of depressing and gripping the strings. This is similar to the convention of the violin family of instruments where the right hand controls the bow. A minority, however, believe that left-handed people should learn to play guitars strung in the manner used by right-handed people, simply to standardise the instrument.

Headstock

The headstock is located at the end of the guitar neck furthest from the body. It is fitted with machine heads that adjust the tension of the strings, which in turn affects the pitch. Traditional tuner layout is "3+3" in which each side of the headstock has three tuners (such as on Gibson Les Pauls). In this layout, the headstocks are commonly symmetrical. Many guitars feature other layouts as well, including six-in-line (featured on Fender Stratocasters) tuners or even "4+2" (Ernie Ball Music Man). However, some guitars (such as Steinbergers) do not have headstocks at all, in which case the tuning machines are located elsewhere, either on the body or the bridge.

Nut

The nut is a small strip of bone, plastic, brass, corian, graphite, stainless steel, or other medium-hard material, at the joint where the headstock meets the fretboard. Its grooves guide the strings onto the fretboard, giving consistent lateral string placement. It is one of the endpoints of the strings' vibrating length. It must be accurately cut, or it can contribute to tuning problems due to string slippage, and/or string buzz.

Fretboard

Also called the fingerboard, the fretboard is a piece of wood embedded with metal frets that comprises the top of the neck. It is flat on classical guitars and slightly curved crosswise on acoustic and electric guitars. The curvature of the fretboard is measured by the fretboard radius, which is the radius of a hypothetical circle of which the fretboard's surface constitutes a segment. The smaller the fretboard radius, the more noticeably curved the fretboard is. Most modern guitars feature a 12" neck radius, while older guitars from the 1960s and 1970s usually feature a 6-8" neck radius. Pinching a string against the fretboard effectively shortens the vibrating length of the string, producing a higher pitch. Fretboards are most commonly made of rosewood, ebony, maple, and sometimes manufactured or composite materials such as HPL or resin. See below on section "Neck" for the importance of the length of the fretboard in connection to other dimensions of the guitar.

Frets

Frets are metal strips (usually nickel alloy or stainless steel) embedded along the fretboard and located at exact points that divide the scale length in accordance with a specific mathematical formula. Pressing a string against a fret determines the strings' vibrating length and therefore its resultant pitch. The pitch of each consecutive fret is defined at a half-step interval on the chromatic scale. Standard classical guitars have 19 frets and electric guitars between 21 to 24 frets (though Ibanez has issued guitars with as many as 36 frets.)

Frets are laid out to a mathematical ratio that results in equal tempered division of the octave. The ratio of the spacing of two consecutive frets is the twelfth root of two. The twelfth fret divides the scale length in two exact halves and the 24th fret position divides the scale length in half yet again. Every twelve frets represents one octave. In practice, luthiers determine fret positions using the constant 17.817, which is derived from the twelfth root of two (2^1/12). The scale length divided by this value yields the distance from the nut to the first fret. That distance is subtracted from the scale length and the result is divided in two sections by the constant to yield the distance from the first fret to the second fret. Positions for the remainder of the frets are calculated in like manner. Actual fret spacing does not use this exact value; the fret spacing on the fretboard was also done by trial and error (testing) method over the ages.

There are several different fret gauges, which can be fitted according to player preference. Among these are "jumbo" frets, which have much thicker gauge, allowing for use of a slight vibrato technique from pushing the string down harder and softer. "Scalloped" fretboards, where the wood of the fretboard itself is "scooped out" between the frets allows a dramatic vibrato effect. Fine frets, much flatter, allow a very low string-action but require other conditions such as curvature of the neck to be well maintained in order to prevent buzz.

On steel-string guitars, frets are eventually bound to wear down; when this happens, frets can be replaced or, to a certain extent, leveled, polished, recrowned, or reshaped as required.

Truss rod

The truss rod is a metal rod that runs along the inside of the neck. It is used to correct changes to the neck's curvature caused by the neck timbers aging, changes in humidity or to compensate for changes in the tension of strings. The tension of the rod and neck assembly is adjusted by a hex nut or an allen-key bolt on the rod, usually located either at the headstock, sometimes under a cover, or just inside the body of the guitar underneath the fretboard and accessible through the sound hole. Some truss rods can only be accessed by removing the neck. The truss rod counteracts the immense amount of tension the strings place on the neck, bringing the neck back to a straighter position. Turning the truss rod clockwise will tighten it, counteracting the tension of the strings and straightening the neck or creating a backward bow. Turning the truss rod counter-clockwise will loosen it, allowing string tension to act on the neck and creating a forward bow. Adjusting the truss rod affects the intonation of a guitar as well as the height of the strings from the fingerboard, called the action. Some truss rod systems, called "double action" truss systems, tighten both ways, allowing the neck to be pushed both forward and backward (standard truss rods can only be released to a point beyond which the neck will no longer be compressed and pulled backward).

Classical guitars do not require truss rods as their nylon strings exert a lower tensile force with lesser potential to cause structural problems. However their necks are often reinforced with a strip of harder wood, such as an ebony strip running down the back of a cedar neck. There is no tension adjustment on this form of reinforcement.

Inlays

Inlays are visual elements set into the exterior surface of a guitar. The typical locations for inlay are on the fretboard, headstock, and on acoustic guitars around the soundhole, known as the rosette. Inlays range from simple plastic dots on the fretboard to intricate works of art covering the entire exterior surface of a guitar (front and back). Some guitar players have used LEDs in the fretboard to produce a unique lighting effects onstage.

Fretboard inlays are most commonly shaped like dots, diamond shapes, parallelograms, or large blocks in between the frets. Dots are usually inlaid into the upper edge of the fretboard in the same positions, small enough to be visible only to the player. These usually appear on the odd numbered frets, but also on the 12th fret (the one octave mark) instead of the 11th and 13th frets. Some older or high-end instruments have inlays made of mother of pearl, abalone, ivory, coloured wood or other exotic materials and designs. Simpler inlays are often made of plastic or painted. High-end classical guitars seldom have fretboard inlays as a well trained player is expected to know his or her way around the instrument.

In addition to fretboard inlay, the headstock and soundhole surround are also frequently inlaid. The manufacturer's logo or a small design is often inlaid into the headstock. Rosette designs vary from simple concentric circles to delicate fretwork mimicking the historic rosette of lutes. Bindings that edge the finger and sound boards are sometimes inlaid. Some instruments have a filler strip running down the length and behind the neck, used for strength and/or to fill the cavity through which the trussrod was installed in the neck.

Elaborate inlays are a decorative feature of many limited edition, high-end and custom-made guitars. Guitar manufacturers often release such guitars to celebrate significant or historic milestones.

Neck

A guitar's frets, fretboard, tuners, headstock, and truss rod, all attached to a long wooden extension, collectively constitute its neck. The wood used to make the fretboard will usually differ from the wood in the rest of the neck. The bending stress on the neck is considerable, particularly when heavier gauge strings are used (see Tuning), and the ability of the neck to resist bending (see Truss rod) is important to the guitar's ability to hold a constant pitch during tuning or when strings are fretted. The rigidity of the neck with respect to the body of the guitar is one determinant of a good instrument versus a poor one. The shape of the neck can also vary, from a gentle "C" curve to a more pronounced "V" curve. There are many different types of neck profiles available, giving the guitarist many options. Some aspects to consider in a guitar neck may be the overall width of the fingerboard, scale (distance between the frets), the neck wood, the type of neck construction (for example, the neck may be glued in or bolted on), and the shape (profile) of the back of the neck. Other type of material used to make guitar necks are graphite (Steinberger guitars), aluminium (Kramer Guitars, Travis Bean and Veleno guitars), or carbon fiber (Modulus Guitars and ThreeGuitars).

Double neck electric guitars have two necks, allowing the musician to quickly switch between guitar sounds.

Neck joint or 'Heel'

This is the point at which the neck is either bolted or glued to the body of the guitar. Almost all acoustic guitars, with the primary exception of Taylors, have glued (otherwise known as set) necks, while electric guitars are constructed using both types.

Commonly used set neck joints include mortise and tenon joints (such as those used by CF Martin & Co. guitars), dovetail joints (also used by CF Martin on the D28 and similar models) and Spanish heel neck joints which are named after the shoe they resemble and commonly found in classical guitars. All three types offer stability. Bolt-on necks, though they are historically associated with cheaper instruments, do offer greater flexibility in the guitar's set-up, and allow easier access for neck joint maintenance and repairs.

Another type of neck, only available for solid body electric guitars, is the neck-through-body construction. These are designed so that everything from the machine heads down to the bridge are located on the same piece of wood. The sides (also known as wings) of the guitar are then glued to this central piece. Some luthiers prefer this method of construction as they claim it allows better sustain of each note. Some instruments may not have a neck joint at all, having the neck and sides built as one piece and the body built around it.

Strings

Modern guitar strings are constructed of metal, polymers, or animal or plant product materials.

Instruments utilising "steel" strings may have strings made of alloys incorporating steel, nickel or phosphor bronze. Classical and flamenco instruments historically used gut strings, but these have been superseded by polymer materials, such as nylon and fluorocarbon materials. Bass strings for both instruments are wound rather than monofilament.

Body (acoustic guitar)

In acoustic guitars, string vibration is transmitted through the bridge and saddle to the body via sound board. The sound board is typically made of tone woods such as spruce or cedar. Timbers for tone woods are chosen for both strength and ability to transfer mechanical energy from the strings to the air within the guitar body. Sound is further shaped by the characteristics of the guitar body's resonant cavity.

In electric guitars, transducers known as pickups convert string vibration to an electric signal, which in turn is amplified and fed to speakers, which vibrate the air to produce the sounds we hear. Nevertheless, the body of the electric guitar still performs a role in shaping the resultant tonal signature.

In an acoustic instrument, the body of the guitar is a major determinant of the overall sound quality. The guitar top, or soundboard, is a finely crafted and engineered element made of tonewoods such as spruce and red cedar. This thin piece of wood, often only 2 or 3 mm thick, is strengthened by differing types of internal bracing. The top is considered by many luthiers to be the dominant factor in determining the sound quality. The majority of the instrument's sound is heard through the vibration of the guitar top as the energy of the vibrating strings is transferred to it.

Body size, shape and style has changed over time. 19th century guitars, now known as salon guitars, were smaller than modern instruments. Differing patterns of internal bracing have been used over time by luthiers. Torres, Hauser, Ramirez, Fleta, and C.F. Martin were among the most influential designers of their time. Bracing not only strengthens the top against potential collapse due to the stress exerted by the tensioned strings, but also affects the resonance characteristics of the top. The back and sides are made out of a variety of timbers such as mahogany, Indian rosewood and highly regarded Brazilian rosewood (Dalbergia nigra). Each one is primarily chosen for their aesthetic effect and can be decorated with inlays and purfling.

The body of an acoustic guitar has a sound hole through which sound is projected. The sound hole is usually a round hole in the top of the guitar under the strings. Air inside the body vibrates as the guitar top and body is vibrated by the strings, and the response of the air cavity at different frequencies is characterised, like the rest of the guitar body, by a number of resonance modes at which it responds more strongly.

Instruments with larger areas for the guitar top were introduced by Martin in an attempt to create louder volume levels. The popularity of the larger "dreadnought" body size amongst acoustic performers is related to the greater sound volume produced.

Body (electric guitar)

Most electric guitar bodies ar