Guitar and Bass Repair – Beyond Basic Tuning – Intonation, What is it and How Does it Work?

Have you ever had a guitar or bass that didn’t quite play in tune no matter how many times you tuned it up? If so, it is quite possible that your instrument’s intonation is incorrect. If you’ve never heard of intonation, read further because it may be the key to making your instrument play in tune. This article will discuss what intonation is, why it needs to be set properly, how to read it and how to make basic adjustments to your instrument’s intonation.

What is Intonation?

The intonation of a guitar or bass has to do with how accurately the instrument voices its notes. A perfectly intonated guitar or bass will play all of its notes with perfect accuracy. An A will be exactly 440hz, and the octave of that A will be exactly 880hz, no matter where it is played on the fretboard. A guitar or bass that is not properly intonated may still sound a perfect A in the open position, but play an A in any other position and it will be slightly out of tune.

On a properly intonated guitar or bass, the length of the string between the nut and saddle will be slightly longer than the instrument’s stated scale length (the theoretical distance from the nut to the saddle). As you fret a string to sound a note it stretches a little, causing its pitch to go slightly sharp. To counteract the change in pitch caused by the stretch, the saddle is placed slightly further back from the fretboard, effectively increasing the length of the string and lowering the pitch. This extra distance the saddle is placed beyond the scale length is called compensation.

A string under lower tension will stretch more than a string under higher tension and will require more compensation to be properly intonated. All things being equal, a guitar or bass with high action, a high nut or lower tension strings will require more compensation than an instrument with low action, a short nut or higher tension strings.

Checking the Intonation of Your Instrument

To see if the intonation of your instrument is set properly, you will first need to obtain a good quality chromatic tuner. You should spend at least $20 on a tuner that you intend to use for reading and setting intonation. A cheap, non-chromatic tuner may produce readings that are inaccurate. If you are reading the intonation of an electric instrument with more than one pickup, plug the tuner into the instrument, make sure the volume and tone controls are turned all the way up and that only the pickup nearest the fretboard is turned on, then follow the steps below:

1. Tune the instrument to pitch.

2. Play the harmonic at the twelfth fret of the low E string and note the reading of the tuner.

3. Now fret the string at the twelfth fret, play the E and note the reading of the tuner.

4. If both the harmonic E and fretted E are exactly in tune with each other, the E-string is properly intonated. If the fretted E is not in tune with the harmonic, the string is not properly intonated and the instrument requires adjustment.

5. Repeat for each string.

Setting the Intonation of Your Instrument

If you’ve never had your instrument set up or intonated, there is a good chance that its intonation is off. If you have an instrument with saddles that adjust forward and back from the fretboard, use the following procedures to adjust your intonation, otherwise skip to “Adjusting Intonation with Fixed Saddle(s)”.guitar tremolo

Note: If you are doing a full setup on an instrument, do not adjust the intonation until all other adjustments have been made first.

Adjusting Intonation with Moveable Saddle(s)

1. Tune your instrument and read the intonation of the low E-string.

2. If the E fretted at the twelfth fret is sharp compared to the harmonic at the twelfth fret, the string requires more compensation and the saddle should be backed away from the fretboard. If the fretted E is flat compared to the harmonic, the string has too much compensation and the saddle should be adjusted towards the fretboard.

3. Adjust the saddle slightly in the proper direction by tightening or loosening the intonation screws found on the rear or front face of your bridge, re-tune the string and check its intonation again.

4. Repeat these procedures until the harmonic E and fretted E are in tune with each other. Repeat for each string.

If you have a fretless instrument you should fret the twelfth fret position with the edge of a credit card, instead of your finger, to get maximum accuracy. If your fretless instrument does not have a marker that designates its twelfth fret position, divide the instrument’s scale length in half and measure that distance from the nut down the fretboard; that is the twelfth fret position. Mark this position with some low-tack tape that will not damage the fretboard or finish, then adjust the intonation.

 

 

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