A fundamental adjustment most guitars need occasionally is the intonation, which can be described as the precise placement of the bridge saddle(s) allowing an instrument to play in tune (or at least as close to “in tune” as a guitar typically gets). This article will delve into this procedure and hopefully give you the ability to tweak your own intonation. The principles discussed are valid for all string instruments, but the procedures for adjusting those instruments vary. We will focus on setting the intonation on a standard electric guitar with individually adjustable string saddles.
First, some theory. There are three factors which determine the pitch of a string:
* Diameter (string gauge – smaller strings produce higher pitches)
* Tension (tuning – greater string tension produces higher pitches)
* Length (scale – shorter strings produce higher pitches)
The neck and fretboard of a guitar constitutes an absolute dimensional reference – while the curvature of the neck can be adjusted, the positions of the frets cannot. In order for a stringed instrument to play in tune, the scale (or, the exact length of the strings) must be precisely adjusted relative to the neck and fretboard of the instrument. So we must compensate at the bridge, adjusting each string saddle to achieve the optimal length of the string so it will be in harmony with the positioning of the frets.
Setting intonation is typically the final tweak you perform on a complete setup of an instrument. First you would want to adjust the neck and overall saddle height before you intonate, since changing any of these factors will generally require re-intonating.
On a whammy-bar guitar, the tension of the whammy springs also should be adjusted before intonating. On a typical Strat-type whammy rig, adjusting the spring tension so that the high E string can go sharp about a whole-step (when the whammy is hard-tailed against the top of the guitar) is about right. You definitely do NOT want to have the springs too loose, or the bridge assembly will lose it’s optimal leverage against the fulcrum, and your guitar will be a pain in the butt to keep in tune.
The gauge of the strings and their pitches all affect the setting of intonation, so these factors must be decided upon prior to any adjustment of intonation. In other words – put on a fresh set of your favorite gauge strings, and tune the guitar to your preferred tuning prior to tweaking your bridge saddles. NOTE: If you change string gauge or tuning scheme later, you will need to reset the intonation.
Basic tools needed are a small screwdriver (or whatever appropriate saddle adjustment tool) and access to a good electronic tuner. The best ones are strobe-type tuners, which are EXTREMELY accurate – and also very pricey. But you can do a decent job with any good-quality, high-resolution guitar tuner.
A Note About Harmonics
You must know how to play “harmonics” on a guitar to intonate it. To play a harmonic, you lightly touch your finger against a string, pick the string, and immediately remove your finger from contact with the string. This will allow both sides of the string to sound at a higher pitch (shorter string lengths affect pitch, remember). Your harmonic location is functioning as a “virtual fret”, if you will.
Not every point on the string will produce a worthwhile harmonic. The “hot spots” are those points on the string where the shorter end of the string, when multiplied by a whole number, equals the total length of the string. So we get strong harmonics when the position of our finger effectively divides the string length in half, in thirds, in fourths, etc. The quality of the harmonic improves as the number of divisions diminishes (thus dividing the string in half produces the strongest harmonic, in thirds less so, and so forth).
In practical terms, if you hit a harmonic directly over the 12th fret, you effectively divide the waveform of the string into two equal parts (from nut to 12th fret, and from 12th fret to bridge), so the string will sound a note *exactly* one octave higher than the open string’s pitch.
Which just happens to be the SAME note that we want to get when we FRET the guitar at the 12th fret. It is thus to this 12th fret harmonic that we adjust the bridge saddle to intonate the string.
OK, the neck is sweet, the saddle height is right-on, the action is ideal, and your axe purrs in your hands – let’s tweak the intonation!
Typical electric guitar adjustable bridge
Lay the axe on its back, with no stress on the neck. Plug it into the electronic tuner. Tune the guitar to pitch. Then do the following procedure for each string:
- Hit a harmonic at the 12th fret.
- Check your tuner and confirm that the harmonic is in perfect tune. If not, adjust the string’s tuning key to bring the harmonic to pitch.
- Fret the string gently at the 12th fret, and sound the note.
- Check the 12th fret note against your tuner and adjust the saddle as needed:
- If the note’s FLAT, the string saddle needs to move TOWARD the neck, which will decrease the length of the string from the 12th fret to the saddle, thus raising the pitch. Use your saddle adjustment tool to adjust the saddle TOWARD the neck.
- If the note’s SHARP, the string saddle needs to move AWAY from the neck, which will increase the length of the string from the 12th fret to the saddle, thus lowering the pitch. Use your saddle adjustment tool to adjust the saddle AWAY from the neck.
After you have intonated all your strings, go back over them to confirm perfect adjustment. When all is well, consider yourself tweaked.
It’s worth noting again that these basic principles hold true for all string instruments, including acoustics, banjos, mandolins, viols, etc etc. When you want to adjust intonation:
* Increase string length to lower pitch.
* Decrease string length to raise pitch.
Now – plug your axe into your amp, crank it up, and PLAY GUITAR IN TUNE! =o)
Copyright 2001 Jeff Foster. All Rights Reserved.