Wilkat's Help Tips© 2001
 

Guitar or Bass -- Correct Your Intonation:

Perhaps the most common problem stringed instrument players come across relates to improper intonation. What is intonation? Simply put, it's the correct string length from bridge to nut, relative to the fret scale and placement. For example, if your instrument has a scale length of 25 1/2" the open string length from the bridge to the nut should measure 25 1/2". In theory this is correct, but in practice it's not quite absolute. Why? Well, the basic reasons are fairly simple:

1. 1.) The length of the instrument's strings will be greater than the actual scale length since the string must be raised above the fingerboard to avoid contact, and this normally requires the strings to be at a slight angle to the fingerboard as the string rises from the nut up to the top of the bridge.
2. 2.) When you fret a note the string angle is increased, as the string is depressed, and the string is also slightly stretched. Naturally the higher up the fingerboard you go, the greater the clearance, and the greater the string string stretches by being depressed.

Although these are minor in nature, they can produce a quite audible effect on the notes played, and can make your instrument sound sourly out of tune. Prime examples of this occur when all the open strings sound perfectly to pitch, but the minute that you play a chord (particularly a bar chord further up the fingerboard), it sounds off. Or, a fretted note will not be in tune with an open string of the same pitch.

NOTE: Many players fear the worst and wonder if their frets have been incorrectly located. This is not usually the case. In can happen, but is "very" rare.

So, to compensate for these factors, the open string length must be adjusted accordingly. Normally this will require the string length to be increased so that it will measure slightly longer than the designed scale length, which is why your string saddle(s) is (are) at an angle to the frets. In addition, with individual saddles, they will not necessarily be aligned in a row, and will normally be staggered. The amount of compensation varies from one instrument to another, and is also affected by the gauge of strings used, therefore it is impossible to provide an exact measurable amount of compensation for each string. Short scale length basses and guitars require the greatest degree of string compensation, whereas the longer scale lengths require less. For example: a six string guitar will commonly have compensation in the range of 0.03" to 0.06" on the treble strings (E, B. & G), whereas the bass strings will be about 0.12" to 0.19" (D, A, & E). On bass guitars, the common range of compensation will be from 0.12" to 0.31".  Again, the type of strings and the gauge will have a direct effect on the amount of compensation required. Heavier gauge strings tend to require less compensation. Ever notice how the unwound G string on a six string with light 0.009" to 0.042" strings often seems difficult to tune? It may sound okay until you play an open D chord, yet the open E chord sounds fine.

What do I do to fix the problem?:

Obviously it's best to get yourself an accurate / reliable electronic tuner to assist with making adjustments, although basic set up can be done with nothing more than a tuning fork and a good ear.

Ideally, we want the note fretted at the 12 Th. fret to be the same as the open string, only one octave higher. The harmonic at the halfway point of the string's scale length (i.e. above the 12 Th. fret) is the correct pitch, but once you depress the string (and stretch it's length), it will tend to go a bit sharp, indicating that the string length must be increased by moving the saddle back, further away from the nut. Test this out by plucking the harmonic at the 12 Th. fret, and then plucking the note on the 12 Th. fret. If the fretted note should happen to be slightly flat, then conversely you will have to shorten the string's length by moving the saddle closer to the nut.

A good place to start is by first setting up the bottom string to the guitar's scale length (i.e. measure the distance from the fingerboard side of the nut, to the point at which the string rests on the saddle--on a 6 string guitar, start with the treble side E, on a 4 string bass, start with the G string).

Now do the harmonic test at the 12 Th. fret, comparing it to the fretted note at the 12 Th. fret, and make the required adjustment as described above. If you measured correctly, the saddle will have to be pulled back a bit to lower the pitch of the fretted note. Using your electronic tuner you will be able to determine if the not is flat or sharp. ( If you don't have a tuner, use a common A 440 concert pitch fork and start by setting up the A string. You'll have to rely on your ears, and perhaps do a bit more trial and error, but you'll get it right). Then you need to check each string the same way by comparing the harmonic and the fretted note at the twelve fret.

Some important points to remember:

Electric guitar and bass strings are influenced by the magnetic pull of the pick ups. Don't adjust them too close to the strings, as they will draw the strings downward and affect the pitch. I see too many guitar players that do this to try and increase the power output and falsely believe they will increase sustain.

The lower the string action, the less the strings will need to be compensated. However, too low a string action will cause annoying buzzing, and make string bending more difficult.

Don't expect every guitar to be perfectly in tune throughout its' entire scale. A bit of error will virtually always be present (after all, you're not playing a harp or a piano !).

Some Final Comments:

Older / worn strings will start to sound off and you may be tempted to fool around with your intonation in an attempt to resolve this. That's fine, but just remember that you'll likely have to readjust intonation when you put on a new set (or if you decide to change to a different gauge). Changing brands can also result in throwing off your intonation, which can result from minor variation in thickness and tensile strength of the materials used.

Ah.......that sounds better! Now let's wail?