The Guitar Player, Jan Vermeer, c. 1672. By the time the Dutch artist painted this oil-on-canvas work depicting a five-course European guitar, the modern ADGBE tuning (sans low E in this case) used today had already evolved.
Why are guitars tuned EADGBE—a series of perfect fourths and a single major third?
Good question, not least because for the past 1,000 years, most everyone seems to have agreed that the most naturally powerful and pleasing-to-the-ear interval is the mighty perfect fifth. All Western music is pretty much based on the hallowed circle of fifths. Stringed instruments such as the violin, cello and mandolin are tuned in fifths.
And yet there’s the guitar—an extremely popular instrument—tuned in a seemingly odd series of ascending perfect fourths and a single major third. From low to high, standard guitar tuning is EADGBE—three intervals of a fourth (low E to A, A to D and D to G), followed by a major third (G to B), followed by one more fourth (B to the high E).
This arrangement was not arrived at and agreed upon just to confuse everyone. Wikipedia editors and contributors sensibly note that 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.” Of the anomalous major third from G to B, it notes that although “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.”
So there’s our answer: The guitar is tuned the way it usually is because it’s simultaneously musically convenient and physically comfortable.
This, by the way, is an arrangement largely settled on hundreds of years ago. When the five-course (course in this sense meaning a pair of strings tuned in unison) guitarra battente first appeared in Italy in the 1500s and gradually replaced the four-course guitar-like instruments dominant since the beginning of the Renaissance a couple centuries earlier, it was tuned ADGBE, as are the top five strings of the modern guitar (the transition from five pairs of strings to six single strings was under way in Europe by the middle of the 17th century). 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’ve resulted in a second string tuned to C and a first string tuned to F. Lowering what would’ve been that high open F by one half step to an open E returned the interval from first string to second string (B) to a perfect fourth.
Don’t just take Wikipedia’s word for it about the sensibility of the arrangement, though. Noted music instructor and former Television guitarist Richard Lloyd once wrote on his website that while the violin and the cello lend themselves nicely to tuning in fifths because of their small scale length, the same doesn’t necessarily hold true on a larger-scale instrument such as a guitar.
“The guitar is a larger-scaled instrument which is played sitting in one’s lap,” Lloyd wrote. “Even though the cello is a larger instrument than the violin, it is played with the neck vertically, which allows the hand to have a little bit easier time reaching for notes. With the guitar sitting in the lap and the neck diagonal to the player, the bend in the wrist starts to make it more difficult to spread out the fingers. So our next best choice for tuning any larger scaled multi-stringed instrument is going to be to tune in fourths, which are a little closer together. On a guitar, a person with a normal-sized hand can reasonably be expected to sound the major third with the pinkie finger while holding down the tonic with the index finger. So it makes sense that the next string should be the fourth.”
Lloyd also astutely noted, however, that if six-string guitars were tuned completely in perfect fourths, you’d wind up with a harmonically discordant arrangement of (low to high) EADGCF. You can see the problem there—E and F are only a half step apart, imposing a naturally irritating interval of a minor second. “This is a god-awful interval,” Lloyd wrote. “And threatens to sour the whole thing.”
Fortunately, since the ADGBE tuning for the top five strings had already been adopted in the 16th century—before a lower sixth string tuned to E was added—such a problematic tuning arrangement was avoided. That lower 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.