Summary:
To get the best intonation from your guitar:
- Get a new setup done if switching string gauges,
- Consider a dedicated summer saddle, and
- Tune octave- and two-octave-harmonics, not fundamentals, on the lower strings.
In my opinion, playing in tune is the single most important quality a guitar must have, and I take pride in building guitars with excellent intonation. However, what this means isn’t as obvious as it initially seems, and there are three important things players should do in order for the intonation to remain true.
- Choose which string gauge (and preferably which specific type) you prefer when your instrument is built or set up. If you decide to switch gauges, put the new strings on and play the guitar over at least a few days, and then bring it back to me for a new setup. I compensate the saddle (and nut when desired) of each guitar specifically for the strings the guitar will be strung with, so switching strings may require a new nut and/or saddle for optimal intonation. However, it’s important not to do the setup with brand new strings, as the intonation can change over the first few days.
- Pay attention to how the intonation of your guitar changes with the seasons. It may need setup adjustments depending on your ambient humidity. I build my guitars at 35% relative humidity, which is a good compromise for temperate climates, but the intonation is likely to go slightly off (and the action to increase) in the summer. If this is the case, I can make you a summer saddle which you can swap out for the regular saddle. If you live in an area with consistently high or low humidity, I can build you a guitar at a humidity level other than 35%.
- When tuning the guitar, don’t tune fundamentals of the lower strings; instead, whether you’re tuning by ear or with an electronic tuner, tune only octave harmonics of open or gently fretted notes. Choose a harmonic not too far from the high E string in pitch. For example, you can tune the fundamental of the open high E, but tune the fifth-fret harmonic of the open low E, sounding the same pitch as the high E.
The third point is the most nuanced, so most of this web page will be devoted to a discussion of inharmonicity, the reason why it’s important to tune this way.
Inharmonicity
The single most important thing players need to do to maximize the potential of my guitars (or other guitars) is to understand the effects of inharmonicity and compensate correctly for them when tuning their guitar. Correcting for inharmonicity may seem unnecessary when many people don’t do it, but bear in mind that musicians with an excellent ear, who tune by ear, have been getting similar results all along without necessarily knowing why.
Inharmonicity is the phenomenon that arises in a real physical vibrating string with mechanical stiffness (as opposed to an idealized theoretical string) that causes harmonics to always sound sharp in relation to the fundamental note. This happens because the physical stiffness of a string limits its ability to vibrate over the entire length of the string. A friend of mine who’s a piano tuner explained it to me as causing the effective length of string to be reduced by a small amount from the actual length, causing the note to sound slightly sharper than the length, mass, and tension alone would predict. When you sound the first harmonic, the effective length of vibrating string is reduced by the same amount, but now in relation to the halved string length, so the note goes more sharp. No matter what harmonic you play, the effective string length is always reduced by the same amount, so the higher the harmonics, the more sharp they sound. This effect is negligible for thin, flexible strings, such as the high E on a steel-string guitar and all the treble strings on a classical guitar. However, for thicker, stiffer strings, such as the low E on any guitar, the effect can be quite noticeable. The best way to reduce the inharmonicity of bass strings is to make them longer, which is the primary reason why concert grand pianos are so large, and also a natural advantage that longer-scale guitars have over shorter-scale guitars.
When we play music that includes bass notes and treble notes together, what our ear hears as in tune is when the upper partials of the bass notes are in tune with the treble notes, not when the fundamentals of the bass notes are in tune with the treble notes. For example, if you tune the high E and the low E on a guitar with an electronic tuner, and then play them together, they don’t sound right. If you have a good ear and you tune the low E by ear to the high E, however, you’ll notice that the electronic tuner tells you the low E is flat. But play the fifth-fret harmonic on the low E and the tuner will tell you it’s right. That’s because your ear tuned that partial, rather than the fundamental, without you even knowing it.
You also might notice that electronic tuners sometimes give weird results. I believe this is because the tuner, like the ear, sometimes picks up on a higher partial when it hears a low note, but it does so in an unpredictable way. For example, when I tune my cello properly, such that the third harmonic of the low C string (which would be the fifth-fret harmonic if there were frets) is in tune, the electronic tuner tells me that the first (twelfth-fret) harmonic is flat, as expected, but it tells me that the fundamental is in tune. The fundamental is in fact quite significantly flat, as a cello C string is much bulkier than any guitar string, so the tuner must be hearing the in-tune third harmonic when I play the fundamental.
When you tune using harmonics, you should only ever use octaves of the open or fretted note. Don’t tune with the seventh-fret harmonics (the interval of a twelfth above the fundamental) if you want your instrument to be tuned to equal temperament. You can use them to tune fretless instruments for certain styles of music, but that’s way beyond the scope of this web page.
Here are two specific sequences of notes to tune, the first using only natural harmonics (works well with an electronic tuner) and the second using all the same pitch (more reliable if tuning by ear). These are not the only options; you can use other sequences if you follow the basic principles outlined above. For example, if you’re starting with an A from another instrument in an ensemble, you might want to build a sequence that starts with the fifth-fret harmonic of the 5th string. Also, on a classical guitar, you can get pretty good results by tuning the fundamentals of the first four strings, and perhaps even the 5th string, but you should still tune the fifth-fret harmonic of the 6th string.
Sequence 1 (electronic tuner)
1st string: tune the fundamental.
2nd string: tune the fundamental.
3rd string: tune the twelfth-fret harmonic.
4th string: tune the twelfth-fret harmonic.
5th string: tune the fifth-fret harmonic.
6th string: tune the fifth-fret harmonic.
Sequence 2 (by ear)
1st string: tune the fundamental.
2nd string: fret at the fifth fret and tune the fundamental.
3rd string: fret at the ninth fret and tune the fundamental.
4th string: fret at the second fret and tune the artificial harmonic at the fourteenth fret (one octave from the fretted note).
5th string: fret at the seventh fret and tune the harmonic at the nineteenth fret (one octave from the fretted note).
6th string: tune the fifth-fret harmonic.
Of course, if you’re tuning by ear, you don’t have to actually play the harmonics you’re tuning; you can play the fundamentals and listen for the harmonics. But if you’re new to this way of tuning it’s a good idea to actually play them to make sure you fully understand what you’re doing.
Choosing a compensated or uncompensated nut
Most guitars have a compensated saddle, but not a compensated nut, and therefore, fretted notes on the lower frets tend to sound a bit sharp. Most of us have gotten used to this sound, so correcting it is an option, but not a necessity. Compensated nuts also look different from normal nuts, so this is a decision I like to discuss with my customers. Another option is a zero fret, which also improves the intonation on the lower frets.
Limitations of fixed frets
Even when a guitar is set up perfectly, straight fixed frets have a limitation. The strings of a guitar, with their varying stiffness, stretch slightly differently when fretted. Therefore, the pitch changes by a different amount for each note. Most of this effect can be corrected by compensating the nut and saddle, but not all. Therefore, the best we can do is make the open strings, first-fret notes, and twelfth-fret notes in tune, and everything else will be close, but not exact. One effect of this is that even on a perfectly set up guitar, the two tuning sequences I described will not give identical results: sequence 1 may make open chords sound better, while sequence 2 may make barre chords and playing up the neck sound better. On a guitar with a compensated nut they’ll be very similar, but on a guitar with an uncompensated nut you’re likely to get better results with sequence 2, because it makes most fretted notes more in tune.
There are guitars with frets that are not straight, but rather compensate for every note independently. If they’re set up perfectly with broken-in strings, and kept at a tightly controlled humidity, these guitars can come close to achieving mathematically perfect 12 tone equal temperament. I don’t do this, but I would be interested in trying it if someone requests it as a custom build. Not everyone likes the sound of such guitars though. The guitar as we know it doesn’t sound mathematically in tune, and to some, this is part of what makes it sound like a guitar. Making it perfect may take away some of the character we love about it.