What Is Guitar Intonation?

Intonation is the accuracy in which a guitar or bass guitar can produce a fretted note. Setting the intonation is the act of adjusting the length of the strings (by moving the bridge saddles) to compensate for the stretching of a string due to pushing it down to the fret board to produce a note. To adjust the intonation of your guitar or bass, you move the bridge saddles toward or away from the fret board until the 12th fret octave and its harmonic are equal and the same open-string note is exactly one octave below those. Accurate intonation is critical to sound quality.

When a guitar or bass guitar has an inaccurate intonation setting, you may notice that chords played at the bottom of the neck sound correct, but the same chord played higher up the fret board have some notes that become out of tune, making the chords sound more like noise than music. An example is that you may play an open A on the 5th (or 3rd) string together with the same note on the 6th (or 4th) string to add depth. If these notes aren't exactly the same, you may think that your instrument is out of tune. That is what this article will try to help you correct.

Check Your Guitar or Bass Intonation

Checking intonation is easy, especially if you have a digital tuner. The best tuners to use for this task are the ones with a meter readout rather than LEDs since it is much easier to see how much adjustment may need to be done. You must also be sure that your strings are new, but you should check your intonation periodically just to be sure that it is correct. First, you must tune your guitar to your desired tuning. Each time you change strings or tunings, your strings' tension or height may change slightly, which may unset your intonation.

With your instrument in the same position as you normally play (playing position), not lying on a table, check the tuning of the natural harmonic at the 12th fret (gently touching the string above the 12th fret while picking). This should be exactly equal to the tuning if you were to push the string down to the fret. If they are the same and you still have intonation problems, check the open strings and the other fretted notes. If particular frets are out of tune while others are in tune across each string, the frets on your instrument may be worn to the point where the string is not contacting the centers of the frets. If that is the case, you may need to grind and polish or replace the worn frets to cure this problem.

If the intonation starts out bad on the first few frets and gets progressively better going up to the 12th fret, your guitar may have a misplaced nut. This would throw the entire scale of your guitar or bass guitar off. It is suggested that you have an instrument repair person replace the nut to ensure that it is in the correct position. If you do have the nut replaced by a repair person, be sure to check their job thoroughly before leaving the shop - even if you have to completely set the intonation right there! If the problem still exists, be sure to explain it to the repair person (you may want to explain the problem before repairs are done as well). Some cheaply made guitars may never be able to correct this problem, but if you are paying to have the nut replaced, be sure what they have done the best job possible - before handing over your hard-earned cash.

Adjust Your Guitar Or Bass Guitar Intonation

Because adjustments such as action (the height of the strings from the fret board), truss rod tightness, string thickness or material and the magnetic pull of your pickups can effect an instrument's intonation, adjustments must be performed as the last step in setting up your guitar or bass guitar. When you are checking the intonation of your instrument, it must be done in your normal playing position in order to correctly account for any neck flex which effects the string height (action).

Adjusting an instrument's intonation consists of setting the bridge saddles to produce the note at the 12th fret exactly an octave higher than that of the open string. With the aid of an electronic or digital tuner, compare either the open string or the octave harmonic at the 12th fret with the fretted octave at the 12th fret. Use slight finger pressure, as any extra pressure ("articulation") will disrupt the accuracy of the adjustment. If the fretted note is sharp, move the saddle away from the pickups and fret board; if it is flat, move the saddle toward the pickups and fret board.

If you periodically check your intonation, adjustments should rarely take more than a few minutes, provided you stick with the same tuning, action and string gauges. Check the intonation every time you change your strings, especially if you are changing tunings, gauges, or even brands. Even the slightest differences between sets of strings can make a noticeable difference.

If your bridge does not provide you with enough adjustment, it may be necessary to have a repair person take a look. Sometimes it may be as simple as the saddle needs to be turned around and re-slotted. In some more extreme cases, the entire bridge may need to be moved.

Factors Causing Inaccurate Or Poor Intonation On A Guitar Or Bass Guitar

If your guitar or bass guitar has poor intonation, you may want to check factors such as your action, bridge saddles or worn frets. The action of your instrument may cause your intonation to be sharp - the higher the action is, the more the strings need to be stretched in order to fret a note. If your bridge saddles are worn or leaning, that may effect the action of your instrument as well as the shorten a string's life.

One other factor that has come up much more often in the last few years involves low tunings. Guitars and bass guitars are made to handle a range of string thicknesses. These string gauges can only produce a certain number of notes. Lower notes will not only loosen the string, but may require you to raise your action to prevent fret buzz. In doing so, you will also make your intonation sharper, possibly causing your bridge saddles to run out of adjustment room. If this is the case, you may (though it is not recommended) need to move your entire bridge away from the nut in order to gain the additional adjustment room required to set your intonation.

Before you consider moving the bridge, try a thicker gauge string (I know many guitarists that use a bass string in place of their low string). If this still doesn't work for you, get a new instrument that can support what you want. For instance, spend the cash to get a 5-string bass or a baritone or 7-string guitar if you have to. After all, homemade, custom-built guitars don't always have an accurate scale, and may cost just as much as a new mass-produced guitar by the time you buy all the pieces. (Trust me, I know this from experience!)