In tracing the general evolution of the guitar, it becomes largely a matter of speculation. We cannot say specifically when one instrument appeared, what influenced its origins, and how it affected the development of other instruments. However, historians can agree on certain basic patterns of progression.

The first instruments that could be considered guitar-like, probably appeared during the Renaissance. But, unlike other instruments of the time, which were varied in shape and size, the bodies of these guitarish instruments were indented in some fashion or other, along the likes of the now accepted hourglass shape, with rounded bouts. It would take another few centuries to arrive at the now standard guitar shapes we enjoy today.

In Spain of the 13th through 15th centuries, two instruments could be called "guitar": the guitarra moresca, a lute shaped instrument; and the guitarra latina, a more guitar like shaped instrument. As this period ended, the instruments were more commonly called guitarra and chitarra. A third instrument, the vihuela de mano was a similar guitar-like instrument, plucked with the fingers. And as the 15th century came to an end, these instruments began to become more rounded and have more prominent indentations at the waist.

As the 16th century opened, the guitarra and vihuela were interchangable terms and would be clearly recognizable to anyone today as a guitar, but with no standard size yet determined. The vihuela was usually strung with six courses (pairs) of strings, with gut frets wound around the neck/fret board. The guitarra, a smaller instrument, had four courses of strings and was fretted in like manner. During the 16th century, a 5 course guitar appeared, and is generally considered to have originated in Spain.

The five course guitar became very popular throughout Europe, eclipsing a four course instrument and the vihuela. In Italy, a version of the chitarra was very popular and had 5 courses of wire strings, and was played with a plectrum (pick).

It was in the 18th century that the guitar began to change features to become the essence of the modern guitar. In France, the waist of the instrument became even more pronounced, perhaps between 1750 and 1770; but in the late 1700s, one of the most important changes in guitar development occurs: the first 6 string guitar. Italy quickly adopted this version. Spain clung to having courses, having moved to the 6 course instruments. And it was during the last decade of the 18th century that José Pagés experimented with different bracing patterns for the six course guitar.

By 1800 the 5 course guitar went the way of History. The whole craft of instrument making went through numerous changes from the mid 1700s to the mid 1800s. Apart from the change from 5 courses to 6 courses, and from double strings to single strings, modern tuning and construction techniques were introduced. We don't know precisely when the six string guitar was adopted in Spain, but there is speculation that it was around 1820 or so. The 6 string guitar gradually became more standardized, and modern features appeared. Wooden pegs became normal for holding the strings in place on the sound board; bone and ivory saddles were intrduced; the modern fret board shape was developed by Georg Staufer, a German luthier. And tuning pegs were replaced by machines just before 1830. An Italian, Louis Panormo, made instruments modeled after those of José Pagés.

Spanish luthier Antonio de torres Juardo is considered the father of the modern Classical guitar, introduced in the 1850s, in Seville, Spain. He introduced large upper and lower bouts, a scale length of 65cm (650mm), a wider and thicker fret board and a less decorative appearance. And he is also credited with originating the 'fan' bracing pattern concept.

So why are guitars tuned EADGBE; a series of perfect fourths and a single major third?

Well, for most of the past 1,000 years, everyone seems to be in agreement that the naturally powerful and pleasing to the ear interval, the mighty perfect fifth, is to be responsible. Western music is based upon the Circle of Fifths. Stringed instruments such as the violin, cello and mandolin are tuned in fifths.

The guitar, just about the most popular instrument in the world, is tuned in an ascending series of perfect fourths with a single major third. From low to high, standard guitar tuning is EADGBE, three of the intervals being in fourths (low E to A, A to D and D to G), then a major third (G to B), and finally by one more fourth (B to the high E).

This tuning was not arrived at and agreed upon by accident. If Wikipedia editors and contributors are to be believed (and I seldom do) the standard guitar tuning "evolved to provide a good compromise between simple fingering for many chords and the ability to play common scales with minimal left hand movement," and that the four pairs of perfect-fourth string intervals produce "a symmetry and intelligibility to fingering patterns." And the major third from G to B? They continue: "...this breaks the fingering pattern of the chromatic scale and thus the symmetry, it eases the playing of some often-used chords and scales, and it provides more diversity in fingering possibilities."

The guitar is (standard) tuned the way it is because it is both musically convenient and physically comfortable.

This goes back hundreds of years. When the 5 course chitarra battente first appeared in the 1500s, it was tuned ADGBE, as are the top five strings of the modern guitar. Tuning the third and second strings (G and B) to a major third interval made fingering easier than continuing a series of perfect fourths, which would have resulted in a second string tuned to C and a first string tuned to F. You would end up with a discordant harmonic arrangement of (low to high) EADGCF. Try tuning your guitar to this and give it whirl.

Since the ADGBE tuning for the top five strings was already "standard" in the 16th century, before a lower sixth string tuned to E was added, such problematic tuning issues were not confronted. The addition of the low E continued the arrangement of perfect fourths used for all string pairs except the major-third interval adopted for the second and third strings, resulting in the standard guitar tuning that remains today.