Why Is the B String the Weird One on a Guitar?

There is a small inconsistency built into almost every normally tuned guitar.

Start with the lowest string. E to A is a perfect fourth. A to D is another fourth. D to G is another. Then the pattern breaks. G to B is a major third. After that, B to the high E returns to a fourth.

In semitones, the pattern is 5, 5, 5, 4, 5.

This is why the B string seems to misbehave when you learn scales, chords or the old fifth fret method of tuning by ear. The B string is not positioned according to the same interval as most of its neighbors.

If every string continued upward by a perfect fourth, the guitar would not be tuned E A D G B E. It would be E A D G C F.

That tuning exists. It is usually called all fourths tuning. The B string moves up to C and the high E moves up to F, leaving exactly five semitones between every pair of neighboring strings.

The result is a much more regular fretboard. A scale or interval pattern does not need the familiar adjustment when it crosses from the G string to the B string. Some guitarists prefer that consistency.

But regularity is not the only thing a guitar tuning has to solve.

A guitar is different from an instrument such as a violin in one important respect. Guitarists routinely hold several fretted notes at once.

Violins, violas and cellos are generally tuned in fifths. That gives them a broad range across relatively few strings. Doing the same thing on a guitar would spread neighboring strings much farther apart in pitch, which would also spread many useful notes farther apart on the fretboard.

Fourth based tuning keeps the strings closer together. Yamaha describes this as one reason guitar chords can be formed without forcing the fretting hand into much larger stretches.

The major third between G and B compresses the layout by one additional semitone. It also contributes to the familiar chord shapes that generations of guitar music have been built around.

There is a tradeoff. Standard tuning makes many chords comfortable, but it makes the fretboard less mathematically consistent. Every guitarist eventually learns to compensate for that one fret shift when a pattern crosses the B string.

It would be neat if there were a single inventor who sat down with six strings and decided that the second one should be B. Guitar history is much messier than that.

The major third appears long before the modern six string instrument.

The Metropolitan Museum of Art describes early four course guitars from the Renaissance whose strings were commonly arranged in the interval pattern fourth, major third, fourth. One example of the pitches is G, C, E, A.

That structure should look familiar. There is already one major third surrounded by fourths.

As guitars developed, the number of courses changed, construction changed and eventually paired strings gave way to the six single strings familiar today.

But part of the tuning pattern stayed remarkably recognizable.

The Met gives A D G B E as a typical tuning for a five course Baroque guitar. Those are the same pitches, in the same interval relationships, as the upper five strings of modern standard tuning.

When six course and then six single string guitars became established, the added bass range produced the E A D G B E arrangement we now call standard tuning.

So the B string is not a strange modern modification to an otherwise perfect system of fourths. The major third was already embedded in the guitar family centuries earlier.

You can.

Tune the B string up to C and the high E up to F and you have E A D G C F, an all fourths guitar. The fretboard becomes more regular. Patterns that cross strings are easier to understand because the same interval separates every adjacent pair.

The cost is that standard guitar vocabulary no longer lines up in the same way. Open chords, barre chords, scale fingerings, riffs and songs learned in EADGBE have to be adjusted.

Centuries of guitar music, teaching and muscle memory are built around standard tuning. Its inconsistency has effectively become part of the instrument.

There is a practical way to see the irregularity without knowing any theory.

When tuning a guitar to itself, the fifth fret of the low E produces A, the pitch of the next open string. The fifth fret of A produces D. The fifth fret of D produces G.

Then the rule suddenly changes.

To find B from the G string, you use the fourth fret, not the fifth. Once you reach the B string, the fifth fret gives you the high E and the old rule returns.

That single fourth fret is the physical consequence of the major third hidden inside EADGBE.

There are more symmetrical ways to tune a guitar. There are tunings with wider ranges. There are tunings that make particular chords dramatically easier.

Standard tuning survived because it balances several jobs reasonably well. It gives the guitar useful range, keeps fretted notes within reach and supports a huge variety of chords and melodies.

The B string is the price of that compromise. It breaks the pattern, but the broken pattern has been part of guitar playing for hundreds of years.

In modern standard tuning, the open strings are E2, A2, D3, G3, B3 and E4. At the common A4 reference of 440 Hz, their frequencies are shown below.