Front and lateral view of a typical modern classical guitar
(Composite chordophone sounded by the bare fingers or fingernails)
|Developed||modern classical guitar was developed in the late 19th century|
The classical guitar (also known as the nylon-string guitar, or Spanish guitar) is a member of the guitar family used in classical music. It is an acoustic wooden guitar with strings made of gut or nylon, rather than the metal strings used in acoustic and electric guitars. For a right-handed player, the traditional classical guitar has twelve frets clear of the body and is properly held on the left leg, so that the hand that plucks or strums the strings does so near the back of the sound hole (this is called the classical position). The modern steel string guitar, on the other hand, usually has fourteen frets clear of the body (see Dreadnought) and is commonly played off the hip.
The phrase "classical guitar" may refer to either of two concepts other than the instrument itself:
The term modern classical guitar is sometimes used to distinguish the classical guitar from older forms of guitar, which are in their broadest sense also called classical, or more specifically, early guitars. Examples of early guitars include the six-string early romantic guitar (c. 1790-1880), and the earlier baroque guitars with five courses.
The materials and the methods of classical guitar construction may vary, but the typical shape is either modern classical guitar or that historic classical guitar similar to the early romantic guitars of France and Italy. Classical guitar strings once made of gut are now made of such polymers as nylon, with fine wire wound about the acoustically lower (bass side) strings.
The classical guitar has a long history and one is able to distinguish various:
Both instrument and repertoire can be viewed from a combination of various perspectives:
Historical (chronological period of time)
While "classical guitar" is today mainly associated with the modern classical guitar design, there is an increasing interest in early guitars; and understanding the link between historical repertoire and the particular period guitar that was originally used to perform this repertoire. The musicologist and author Graham Wade writes:
Nowadays it is customary to play this repertoire on reproductions of instruments authentically modelled on concepts of musicological research with appropriate adjustments to techniques and overall interpretation. Thus over recent decades we have become accustomed to specialist artists with expertise in the art of vihuela (a 16th-century type of guitar popular in Spain), lute, Baroque guitar, 19th-century guitar, etc.
Different types of guitars have different sound aesthetics, e.g. different colour-spectrum characteristics (the way the sound energy is spread in the fundamental frequency and the overtones), different response, etc. These differences are due to differences in construction; for example modern classical guitars usually use a different bracing (fan-bracing) from that used in earlier guitars (they had ladder-bracing); and a different voicing was used by the luthier.
There is a historical parallel between musical styles (baroque, classical, romantic, flamenco, jazz) and the style of "sound aesthetic" of the musical instruments used, for example: Robert de Visée played a baroque guitar with a very different sound aesthetic from the guitars used by Mauro Giuliani and Luigi Legnani - they used 19th century guitars. These guitars in turn sound different from the Torres models used by Segovia that are suited for interpretations of romantic-modern works such as Moreno Torroba.
When considering the guitar from a historical perspective, the musical instrument used is as important as the musical language and style of the particular period. As an example: It is impossible to play a historically informed de Visee or Corbetta (baroque guitarist-composers) on a modern classical guitar. The reason is that the baroque guitar used courses, which are two strings close together (in unison), that are plucked together. This gives baroque guitars an unmistakable sound characteristic and tonal texture that is an integral part of an interpretation. Additionally the sound aesthetic of the baroque guitar (with its strong overtone presence) is very different from modern classical type guitars, as is shown below.
Today's use of Torres and post-Torres type guitars for repertoire of all periods is sometimes critically viewed: Torres and post-Torres style modern guitars (with their fan-bracing and design) have a thick and strong tone, very suitable for modern-era repertoire. However, they are considered to emphasize the fundamental too heavily (at the expense of overtone partials) for earlier repertoire (Classical/Romantic: Carulli, Sor, Giuliani, Mertz, ...; Baroque: de Visee, ...; etc.). "Andrés Segovia presented the Spanish guitar as a versatile model for all playing styles" to the extent, that still today, "many guitarists have tunnel-vision of the world of the guitar, coming from the modern Segovia tradition".
While fan-braced modern classical Torres and post-Torres style instruments coexisted with traditional ladder-braced guitars at the beginning of the 20th century, the traditional forms eventually fell away. Some attribute this to the popularity of Segovia, considering him "the catalyst for change toward the Spanish design and the so-called 'modern' school in the 1920s and beyond." The styles of music performed on ladder-braced guitars were becoming more and more unfashionable; and, e.g. in Germany, musicians were in part turning towards folk music (Schrammel-music and the Contraguitar), but this only remained localized in Germany and Austria and became unfashionable again. On the other hand, Segovia was playing in concerts around the world, popularizing his modern classical guitar, as well as a new style of music in the 1920s: Spanish romantic-modern style with guitar works by Moreno Torroba, de Falla, etc. Some people consider it to have been this influence of Segovia which led to the domination of the Torres instrument. Factories all over the world began producing them in large numbers.
It was the 19th century classical guitarist Francisco Tárrega who first popularized the Torres design as a classical solo instrument.
From approximately 1780 to 1850, the guitar had numerous composers and performers including:
Hector Berlioz studied the guitar as a teenager,Franz Schubert owned at least two and wrote for the instrument,Ludwig van Beethoven, after hearing Giuliani play, commented the instrument was "a miniature orchestra in itself".Niccolò Paganini was also a guitar virtuoso and composer. He once wrote: "I love the guitar for its harmony; it is my constant companion in all my travels". He also said, on another occasion: "I do not like this instrument, but regard it simply as a way of helping me to think" 
The guitarist and composer Francisco Tárrega (b. Vilareal, Spain in November 29, 1852-d. December 15, 1909) was one of the great guitar virtuosos and teachers and is considered the father of modern classical guitar playing. As professor of guitar at the conservatories of Madrid and Barcelona, he defined many elements of the modern classical technique and elevated the importance of the guitar in the classical music tradition.
At the beginning of the 1920s, Andrés Segovia popularized the guitar with tours and early phonograph recordings. Segovia collaborated with the composers Federico Moreno Torroba and Joaquin Turina with the aim of extending the guitar repertoire with new music. Segovia's tour of South America revitalized public interest in the guitar and helped the guitar music of Manuel Ponce and Heitor Villa-Lobos reach a wider audience. The composers Alexandre Tansman and Mario Castelnuovo-Tedesco were commissioned by Segovia to write new pieces for the guitar.Luiz Bonfá popularized Brazilian musical styles such as the newly created Bossa Nova, which was well received by audiences in the USA.
The classical guitar repertoire also includes modern contemporary works - sometimes termed "New Music" - such as Elliott Carter's Changes,Cristóbal Halffter's Codex I,Luciano Berio's Sequenza XI,Maurizio Pisati's Sette Studi,Maurice Ohana's Si Le Jour Paraît,Sylvano Bussotti's Rara (eco sierologico),Ernst Krenek's Suite für Guitarre allein, Op. 164,Franco Donatoni's Algo: Due pezzi per chitarra, etc.
Performers who are known for including modern repertoire include Jürgen Ruck, Elena Càsoli, Leo Brouwer (when he was still performing), John Schneider, Reinbert Evers, Maria Kämmerling, Siegfried Behrend, David Starobin, Mats Scheidegger, Magnus Andersson, etc.
This type of repertoire is usually performed by guitarists who have particularly chosen to focus on the avant-garde in their performances.
Within the contemporary music scene itself, there are also works which are generally regarded as extreme. These include works such as Brian Ferneyhough's Kurze Schatten II,Sven-David Sandström's away from and Rolf Riehm's Toccata Orpheus, etc. which are notorious for their extreme difficulty.
The evolution of the classical guitar and its repertoire spans more than four centuries. It has a history that was shaped by contributions from earlier instruments, such as the lute, the vihuela, and the baroque guitar.
The last guitarist to follow in Segovia's footsteps was Julian Bream and Julian Bream will be 73 years old on July 15th 2006. Miguel Llobet, Andrés Segovia and Julian Bream are the three performer personalities of the 20th century. Do not understand me wrong, we have many guitarists today that are very excellent performers, but none with such a distinct personality in their tone and style as Llobet, Segovia and Bream. In all instrumental areas, not just the guitar, there is a lack of individualism with a strong tendency to conformity. This I find very unfortunate since art (music, theatre or the pictorial arts) is a very individual and personal matter.-- Bernard Hebb, Interview
The origins of the modern guitar are not known with certainty. Some believe it is indigenous to Europe, while others think it is an imported instrument. Guitar-like instruments appear in ancient carvings and statues recovered from Egyptian, Sumerian, and Babylonian civilizations. This means that the contemporary Iranian instruments such as the tanbur and setar are distantly related to the European guitar, as they all derive ultimately from the same ancient origins, but by very different historical routes and influences.
During the late Middle Ages, gitterns called "guitars" were in use, but their construction and tuning was different from modern guitars. The Guitarra Latina in Spain, had curved sides and a single hole. The Guitarra Morisca, which appears to have had Moorish influences, had an oval soundbox and many sound holes on its soundboard. By the 15th century, a four course double-string instrument called the vihuela de mano, that had tuning like the later modern guitar except on one string and similar construction, first appeared in Spain and spread to France and Italy. In the 16th century, a fifth double-string was added. During this time, composers wrote mostly in tablature notation. In the middle of the 16th century, influences from the vihuela and the renaissance guitar were combined and the baroque five string guitar appeared in Spain. The baroque guitar quickly superseded the vihuela in popularity in Spain, France and Italy and Italian players and composers became prominent. In the late 18th century the six string guitar quickly became popular at the expense of the five string guitars. During the 19th century the Spanish luthier and player Antonio de Torres gave the modern classical guitar its definitive form, with a broadened body, increased waist curve, thinned belly, improved internal bracing. The modern classical guitar replaced an older form for the accompaniment of song and dance called flamenco, and a modified version, known as the flamenco guitar, was created.
Alonso de Mudarra's book Tres Libros de Música, published in Spain in 1546, contains the earliest known written pieces for a four-course guitarra. This four-course "guitar" was popular in France, Spain, and Italy. In France this instrument gained popularity among aristocrats. A considerable volume of music was published in Paris from the 1550s to the 1570s: Simon Gorlier's Le Troysième Livre... mis en tablature de Guiterne was published in 1551. In 1551 Adrian Le Roy also published his Premier Livre de Tablature de Guiterne, and in the same year he also published Briefve et facile instruction pour apprendre la tablature a bien accorder, conduire, et disposer la main sur la Guiterne. Robert Ballard, Grégoire Brayssing from Augsburg, and Guillaume Morlaye (c. 1510 - c. 1558) significantly contributed to its repertoire. Morlaye's Le Premier Livre de Chansons, Gaillardes, Pavannes, Bransles, Almandes, Fantasies - which has a four-course instrument illustrated on its title page - was published in partnership with Michel Fedenzat, and among other music, they published six books of tablature by lutenist Albert de Rippe (who was very likely Guillaume's teacher).
The written history of the classical guitar can be traced back to the early 16th century with the development of the vihuela in Spain. While the lute was then becoming popular in other parts of Europe, the Spaniards did not take to it well because of its association with the Moors. Instead, the lute-like vihuela appeared with two more strings that gave it more range and complexity. In its most developed form, the vihuela was a guitar-like instrument with six double strings made of gut, tuned like a modern classical guitar with the exception of the third string, which was tuned half a step lower. It has a high sound and is rather large to hold. Few have survived and most of what is known today comes from diagrams and paintings.
The earliest extant six-string guitar is believed to have been built in 1779 by Gaetano Vinaccia (1759 - after 1831) in Naples, Italy; however, the date on the label is a little ambiguous. The Vinaccia family of luthiers is known for developing the mandolin. This guitar has been examined and does not show tell-tale signs of modifications from a double-course guitar. The authenticity of guitars allegedly produced before the 1790s is often in question. This also corresponds to when Moretti's 6-string method appeared, in 1792.
The modern classical guitar is usually played in a seated position, with the instrument resting on the left lap - and the left foot placed on a footstool. Alternatively - if a footstool is not used - a guitar support can be placed between the guitar and the left lap (the support usually attaches to the instrument's side with suction cups). (There are of course exceptions, with some performers choosing to hold the instrument another way.)
Right-handed players use the fingers of the right hand to pluck the strings, with the thumb plucking from the top of a string downwards (downstroke) and the other fingers plucking from the bottom of string upwards (upstroke). The little finger in classical technique as it evolved in the 20th century is used only to ride along with the ring finger without striking the strings and to thus physiologically facilitate the ring finger's motion.
In contrast, Flamenco technique, and classical compositions evoking Flamenco, employ the little finger semi-independently in the Flamenco four-finger rasgueado, that rapid strumming of the string by the fingers in reverse order employing the back of the fingernail--a familiar characteristic of Flamenco.
Flamenco technique, in the performance of the rasgueado also uses the upstroke of the four fingers and the downstroke of the thumb: the string is hit not only with the inner, fleshy side of the fingertip but also with the outer, fingernail side. This was also used in a technique of the vihuela called dedillo which has recently begun to be introduced on the classical guitar.
Some modern guitarists, such as ?t?pán Rak and Kazuhito Yamashita, use the little finger independently, compensating for the little finger's shortness by maintaining an extremely long fingernail. Rak and Yamashita have also generalized the use of the upstroke of the four fingers and the downstroke of the thumb (the same technique as in the rasgueado of the Flamenco: as explained above the string is hit not only with the inner, fleshy side of the fingertip but also with the outer, fingernail side) both as a free stroke and as a rest stroke.
As with other plucked instruments (such as the lute), the musician directly touches the strings (usually plucking) to produce the sound. This has important consequences: Different tone/timbre (of a single note) can be produced by plucking the string in different manners and in different positions. For example, plucking an open string will sound brighter than playing the same note(s) on a fretted position (which would have a warmer tone).
The instrument's versatility means it can create a variety of tones, but this also makes the instrument harder to learn than a standard acoustic guitar.
In guitar scores the five fingers of the right-hand (which pluck the strings) are designated by the first letter of their Spanish names namely p = thumb (pulgar), i = index finger (índice), m = middle finger (mayor), a = ring finger (anular), c = little finger or pinky (meñique/chiquito)
The four fingers of the left hand (which stop the strings) are designated 1 = index, 2 = major, 3 = ring finger, 4 = little finger; 0 designates an open string, that is a string that is not stopped by a finger of the left hand and whose full length thus vibrates when plucked. On the classical guitar thumb of the left hand is never used to stop strings from above (as is done on the electric guitar): the neck of a classical guitar is too wide and the normal position of the thumb used in classical guitar technique do not make that possible.
Scores (contrary to tablatures) do not systematically indicate the string to be plucked (although in most cases the choice is obvious). When an indication of the string is required the strings are designated 1 to 6 (from the 1st the high E to the 6th the low E) with figures 1 to 6 inside circles.
The positions (that is where on the fretboard the first finger of the left hand is placed) are also not systematically indicated, but when they are (mostly in the case of the execution of barrés) these are indicated with Roman numerals from the first position I (index finger of the left hand placed on the 1st fret: F-B flat-E flat-A flat-C-F) to the twelfth position XII (the index finger of the left hand placed on the 12th fret: E-A-D-G-B-E; the 12th fret is placed where the body begins) or even higher up to position XIX (the classical guitar most often having 19 frets, with the 19th fret being most often split and not being usable to fret the 3rd and 4th strings).
To achieve tremolo effects and rapid, fluent scale passages, the player must practice alternation, that is, never plucking a string with the same finger twice in a row. Using p to indicate the thumb, i the index finger, m the middle finger and a the ring finger, common alternation patterns include:
Music written specifically for the classical guitar dates from the addition of the sixth string (the baroque guitar normally had five pairs of strings) in the late 18th century.
A guitar recital may include a variety of works, e.g. works written originally for the lute or vihuela by composers such as John Dowland (b. England 1563) and Luis de Narváez (b. Spain c. 1500), and also music written for the harpsichord by Domenico Scarlatti (b. Italy 1685), for the baroque lute by Sylvius Leopold Weiss (b. Germany 1687), for the baroque guitar by Robert de Visée (b. France c. 1650) or even Spanish-flavored music written for the piano by Isaac Albéniz (b. Spain 1860) and Enrique Granados (b. Spain 1867). The most important composer who did not write for the guitar but whose music is often played on it is Johann Sebastian Bach (b. Germany 1685), whose baroque lute works have proved highly adaptable to the instrument.
Of music written originally for guitar, the earliest important composers are from the classical period and include Fernando Sor (b. Spain 1778) and Mauro Giuliani (b. Italy 1781), both of whom wrote in a style strongly influenced by Viennese classicism. In the 19th century guitar composers such as Johann Kaspar Mertz (b. Slovakia, Austria 1806) were strongly influenced by the dominance of the piano. Not until the end of the nineteenth century did the guitar begin to establish its own unique identity. Francisco Tárrega (b. Spain 1852) was central to this, sometimes incorporating stylized aspects of flamenco's Moorish influences into his romantic miniatures. This was part of late 19th century mainstream European musical nationalism. Albéniz and Granados were central to this movement; their evocation of the guitar was so successful that their compositions have been absorbed into standard guitar repertoire.
The steel-string and electric guitars characteristic to the rise of rock and roll in the post-WWII era became more widely played in North America and the English speaking world. Agustín Barrios Mangoré of Paraguay composed many works and brought into the mainstream the characteristics of Latin American music, as did the Brazilian composer Heitor Villa-Lobos. Andrés Segovia commissioned works from Spanish composers such as Federico Moreno Torroba and Joaquín Rodrigo, Italians such as Mario Castelnuovo-Tedesco and Latin American composers such as Manuel Ponce of Mexico. Other prominent Latin American composers are Leo Brouwer of Cuba, Antonio Lauro of Venezuela and Enrique Solares of Guatemala. Julian Bream of Britain managed to get nearly every British composer from William Walton to Benjamin Britten to Peter Maxwell Davies to write significant works for guitar. Bream's collaborations with tenor Peter Pears also resulted in song cycles by Britten, Lennox Berkeley and others. There are significant works by composers such as Hans Werner Henze of Germany, Gilbert Biberian of England and Roland Chadwick of Australia.
The classical guitar also became widely used in popular music and rock & roll in the 1960s after guitarist Mason Williams popularized the instrument in his instrumental hit Classical Gas. Guitarist Christopher Parkening is quoted in the book Classical Gas: The Music of Mason Williams as saying that it is the most requested guitar piece besides Malagueña and perhaps the best known instrumental guitar piece today. In the field of New Flamenco, the works and performances of Spanish composer and player Paco de Lucía are known worldwide.
Not many classical guitar concertos were written through the guitar history. Nevertheless, some guitar concertos are nowadays wide known and popular, especially Joaquín Rodrigo's Concierto de Aranjuez (with the famous theme from 2nd movement) and Fantasía para un gentilhombre. Composers, who also wrote famous guitar concertos are: Antonio Vivaldi (originally for mandolin or lute), Mauro Giuliani, Heitor Villa-Lobos, Mario Castelnuovo-Tedesco, Manuel Ponce, Leo Brouwer, Lennox Berkeley... Nowadays, more and more contemporary composers decide to write a guitar concerto.
The classical guitar is distinguished by a number of characteristics:
The fretboard (also called the fingerboard) is a piece of wood embedded with metal frets that constitutes the top of the neck. It is flat or slightly curved. 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. Fretboards are most commonly made of ebony, but may also be made of rosewood, some other hardwood, or of phenolic composite ("micarta").
Frets are the metal strips (usually nickel alloy or stainless steel) embedded along the fingerboard and placed at points that divide the length of string mathematically. The strings' vibrating length is determined when the strings are pressed down behind the frets. Each fret produces a different pitch and each pitch spaced a half-step apart on the 12 tone scale. The ratio of the widths of two consecutive frets is the twelfth root of two (), whose numeric value is about 1.059463. The twelfth fret divides the string in two exact halves and the 24th fret (if present) divides the string in half yet again. Every twelve frets represents one octave. This arrangement of frets results in equal tempered tuning.
A classical guitar's frets, fretboard, tuners, headstock, all attached to a long wooden extension, collectively constitute its neck. The wood for the fretboard usually differs from the wood in the rest of the neck. The bending stress on the neck is considerable, particularly when heavier gauge strings are used.
This is the point where the neck meets the body. In the traditional Spanish neck joint the neck and block are one piece with the sides inserted into slots cut in the block. Other necks are built separately and joined to the body either with a dovetail joint, mortise or flush joint. These joints are usually glued and can be reinforced with mechanical fasteners. Recently many manufacturers use bolt on fasteners. Bolt on neck joints were once associated only with less expensive instruments but now some top manufacturers and hand builders are using variations of this method. Some people believed that the Spanish style one piece neck/block and glued dovetail necks have better sustain, but testing has failed to confirm this. While most traditional Spanish style builders use the one piece neck/heel block, Fleta, a prominent Spanish builder, used a dovetail joint due to the influence of his early training in violin making. One reason for the introduction of the mechanical joints was to make it easier to repair necks. This is more of a problem with steel string guitars than with nylon strings, which have about half the string tension. This is why nylon string guitars often don't include a truss rod either.
The body of the instrument is a major determinant of the overall sound variety for acoustic guitars. The guitar top, or soundboard, is a finely crafted and engineered element often made of spruce, red cedar, redwood or mahogany. This thin (often 2 or 3 mm thick) piece of wood, strengthened by different types of internal bracing, is considered the most prominent factor in determining the sound quality of a guitar. The majority of the sound is caused by vibration of the guitar top as the energy of the vibrating strings is transferred to it. Different patterns of wood bracing have been used through the years by luthiers (Torres, Hauser, Ramírez, Fleta, and C.F. Martin being among the most influential designers of their times); to not only strengthen the top against collapsing under the tremendous stress exerted by the tensioned strings, but also to affect the resonation of the top. Some contemporary guitar makers have introduced new construction concepts such as "double-top" consisting of two extra-thin wooden plates separated by Nomex, or carbon-fiber reinforced lattice - pattern bracing. The back and sides are made out of a variety of woods such as mahogany, maple, cypress Indian rosewood and highly regarded Brazilian rosewood (Dalbergia nigra). Each one is chosen for its aesthetic effect and structural strength, and such choice can also play a significant role in determining the instrument's timbre. These are also strengthened with internal bracing, and decorated with inlays and purfling.
The body of a classical guitar is a resonating chamber that projects the vibrations of the body through a sound hole, allowing the acoustic guitar to be heard without amplification. The sound hole is normally a single round hole in the top of the guitar (under the strings), though some have different placement, shapes, or numbers of holes. How much air an instrument can move determines its maximum volume.
The top, back and sides of a classical guitar body are very thin, so a flexible piece of wood called kerfing (because it is often scored, or kerfed so it bends with the shape of the rim) is glued into the corners where the rim meets the top and back. This interior reinforcement provides 5 to 20 mm of solid gluing area for these corner joints.
During final construction, a small section of the outside corners is carved or routed out and filled with binding material on the outside corners and decorative strips of material next to the binding, which are called purfling. This binding serves to seal off the endgrain of the top and back. Binding and purfling materials are generally made of either wood or high quality plastic materials.
The main purpose of the bridge on a classical guitar is to transfer the vibration from the strings to the soundboard, which vibrates the air inside of the guitar, thereby amplifying the sound produced by the strings. The bridge holds the strings in place on the body. Also, the position of the saddle, usually a strip of bone or plastic that supports the strings off the bridge, determines the distance to the nut (at the top of the fingerboard).
The modern full size classical guitar has a scale length of around 650 mm (26 in), with an overall instrument length of 965-1,016 mm (38.0-40.0 in). The scale length has remained quite consistent since it was chosen by the originator of the instrument, Antonio de Torres. This length may have been chosen because it's twice the length of a violin string. As the guitar is tuned to one octave below that of the violin, the same size gut could be used for the first strings of both instruments.
Smaller-scale instruments are produced to assist children in learning the instrument as the smaller scale leads to the frets being closer together, making it easier for smaller hands. The scale-size for the smaller guitars is usually in the range 484-578 mm (19.1-22.8 in), with an instrument length of 785-915 mm (30.9-36.0 in). Full-size instruments are sometimes referred to as 4/4, while the smaller sizes are 3/4, 1/2 or 1/4.
These sizes are not absolute, as luthiers may choose variations around these nominal scale-lengths;
Guitars can be described in size from largest to smallest as: - Contra or Octave bass; - Bass baritone or Quint bass; - Prime or Quart bass; - Terz treble; - Alto Requinto; - Quart; - Quint; - Soprano, Octave or Piccolo.
A variety of different tunings are used. The most common by far, which one could call the "standard tuning" is:
The above order, is the tuning from the 1st string (highest-pitched string e'--spatially the bottom string in playing position) to the 6th string - lowest-pitched string E--spatially the upper string in playing position, and hence comfortable to pluck with the thumb.
The explanation for this "asymmetrical" tuning (in the sense that the maj 3rd is not between the two middle strings as say in the tuning of the viola da gamba) is probably that the guitar originated as a 4-string instrument (actually an instrument with 4 double courses of strings, see above) with a maj 3rd between the 2nd and 3rd strings and that it only became a 6-string instrument by gradual addition of a 5th string and then a 6th string tuned a 4th apart:
"The development of the modern tuning can be traced in stages. One of the tunings from the 16th century is C-F-A-D. This is equivalent to the top four strings of the modern guitar tuned a tone lower. However, the absolute pitch for these notes is not equivalent to modern "concert pitch". The tuning of the four-course guitar was moved up by a tone and toward the end of the 16th century, five-course instruments were in use with an added lower string tuned to A. This produced A-D-G-B-E, one of a wide number of variant tunings of the period. The low E string was added during the 18th century."
|String||Sci. pitch||Helmholtz pitch||Interval from middle C||Semitones from A440||Freq., if using an Equal temperament tuning (using )|
|1st (highest pitch)||E4||e'||major third above||-5||329.63 Hz|
|2nd||B3||b||minor second below||-10||246.94 Hz|
|3rd||G3||g||perfect fourth below||-14||196.00 Hz|
|4th||D3||d||minor seventh below||-19||146.83 Hz|
|5th||A2||A||minor tenth below||-24||110 Hz|
|6th (lowest pitch)||E2||E||minor thirteenth below||-29||82.41 Hz|
This tuning is such that neighboring strings are at most 5 semitones apart. There are also a variety of commonly used alternate tunings.
A rather small sized vaulted-back guitar in the engraving by Etienne Picart (c. 1680) after the painting by Leonello Spada Concert (c.1615), Musée du Louvre, Paris