Guitar Tuning is Imperfect (Part 2 of 2): Tuning Methods

If you've ever tried tuning a guitar, you might have come across various techniques for doing so. Some common methods include tuning by fretting, by harmonics and by electronic tuner. These methods do not produce identical results, and here we'll take a look at the differences.

Standard guitars are intended to be tuned using equal temperament (as opposed to just temperament), meaning that any two equivalent intervals regardless of the choice of key have equal harmonic relationships. For example, an equally tempered major third in the key of C consists of a C and an E with a frequency difference of 400 cents, and an equally tempered major third in the key of G consists of a G and a B also with a difference of 400 cents. Part 1 gives a bit of background on equal temperament and just temperament which you can read for more details.

Now, let's compare some tuning methods and the results they produce.

Fretting

Fretting might be one of the more common methods of tuning guitars by ear. This method starts with one of the guitar strings tuned properly (by any method), say the low E string. Then, you would fret the E string at the 5th fret and sound the string (to produce an A) and play the A string. While these two tones play together you can tune the A string until it matches the fretted E string. This process continues analogously to tune the remaining strings.

Tuning by fretting inherently relies on the intonation of you guitar, meaning how well the guitar stays in tune as you play on the fretboard. Since guitars are designed to played with equal temperament, the fretting method produces an equally tempered tuning.

Harmonics

Another by-ear method you might come across is tuning by harmonics. Similar to tuning by fretting, you'll first tune one of the strings by whatever method you like, again say the low E string. Then, you'll play an open harmonic on fret 12 of the E string on fret 7 of the A string. These will both produce E notes, and then you can tune the A string — as the harmonics ring out — so that it matches the E string harmonic.

One benefit that proponents of this method claim is that, since harmonics produce a clean tone without overtones, it's easier to detect when the two strings are in tune with each other. While it's true that it's easier to detect the beat frequencies produced by two slightly out-of-tune harmonics, this benefit comes at a cost: The harmonic method produces a justly tempered tuning. Since guitars are tuned in equal temperament, this technically results in an out of tune guitar. In fact, the resulting tuning is different enough that the G and B strings played together exceed the just-noticeable difference. This means that at least 50% of people can hear the difference in the sound produced by G an B strings when equally tempered versus when justly tempered. See Part 1 for some calculations explaining this in more detail.

Electronic Tuner

If you decide to forgo tuning by ear all together, you'd likely purchase an electronic guitar tuner. Since these devices are designed specifically for guitars, electronic tuners produce an equally tempered tuning, just as the fretting method.

But electronic tuners have one leg up on fretting. Tuners avoid iterative error. Simply put, when you tune by fretting, you first tune the A string based on the low E string, then tune the D string based on the A string and continue onward to the high E string. The tuning of each string depends on the tuning of the previous string. If you make a slight error tuning one of the strings, this error will carry through when tuning all of the remaining strings (hence the term "iterative" error). Tuners avoid iterative error by giving an absolute reference of correct pitch via their internal programming.

Consensus

If you intend to tune your guitar by ear, then you'd be better off using the fretting method than the harmonic method, since the harmonic method results in a technically different (though very close to correct) tuning. But if you have access to an electronic tuner, this will provide correct tuning while helping to avoid iterative error.