The guitar that inspired my trading up experiment, Taylor 714ce intonation test results.

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I'm dreaming of a Taylor 714ce guitar.

Why would anyone need a $2800 guitar?? In my case, I've realized as I'm working on perfect "absolute" pitch, that the guitars I have now are out of tune on some notes.

I never thought to check before, but using the free AP Guitar Tuner for Windows--or any other analog chromatic tuner-- you can do this with your own guitar. Tune each open string perfectly, then  check each fretted note. Some of my fretted notes are out of tune. This finally explains why, even when perfectly tuned, my chords don't sound right sometimes.

Anyway,  I played some shows with Jason Mraz before he hit it big and Jason is my ear guru. This is the guitar he plays, so I'm expecting that it will play in tune beautifully.

Taylor 714ce Intonation Experiment Results:  At Skip's Music in Sacramento today 12/14/08, I brought my laptop in and used the AP guitar tuner to check every fretted note on a Taylor 614ce and a 714ce. The 614 was off as much as my Martin, but the 714ce's fretted notes were all within 5 cents of true. Beautiful. The action was great too.

Action test:  Play Van Halen's Spanish Fly if you can learn it from tab. It is a real workout.  There are many people imitating Eddie from transcriptions, but listen to his extended in concert solos and you'll hear the raw creativity that shows his genius. Van Halen was the first band I saw in concert. Though some connections, someone who ran sound for Jason Mraz, I obtained a rare bootleg version of EVH testing some guitars in a store playing Hotel California and some other stuff.  So cool. I used to have dreams he was teaching me stuff and when I woke up I could remember it.

Anyway, getting back to intonation, I've known that the fretted note on the 12th fret should be the same as the harmonic on the 12th fret, and that the bridge positioning determines this, but what if some notes are out and some notes aren't as you move up the fredboard?

Would this always be due to incorrect spacing of frets? If the G note played on the 3rd fret is off, would the other notes on the 3rd fret be off as well? C, F, Bb, D, G.

Experiment Results: No, that isn't the case. With my Martin DM 769325 the G on the 3rd fret is sharp 15 cents, when the low E is in tune, but the other notes are dead on or are only off about 5 cents on the other strings when they are perfectly tuned.

Between one note and the next on a chromatic scale, there are 100 cents. Half way between a B and a C note is a quarter tone, 50 cents. The human ear can detect an instrument which is out of tune by 7 cents or more. This is why my G chords never sound just right on my Martin.

Here are the factors influencing intonation adapted from fretnotguitarrepair:

Incorrect positioning of the saddle or bridge
If the strings are too long the intonation is flat. If too short, the instrument will play sharp when the open strings are perfectly tuned. My E is off 25 cents, A is off 20 cents,  D is of 15 cents,  G is off 5 cents, B is off 20 cents, high E is off 10 cents.

Grooves in the saddle or bridge from wear and tear
Grooves worn down where each string rests on the bridge will change the string length and throw off the intonation.

High action
If the strings are too high off of the fretboard, the stretching before contact sharpens the note slightly. High action at the nut causes chords with notes fretted on the 1st to 3rd frets to sound terribly out of tune.  This may be contributing to my problem with the G note.

Excessive Relief
The strings distance to the fret can be dramatically increased on necks that are too bowed.  A truss rod adjustment can fix this problem. Tighten to rod to reduce excess relief (aka arching, or bowing) or loosen it if your neck is too straight. Some archg is needed to keep the strings from buzzing because they vibrate in an elliptical pattern. See my exaggerated illustration:

Fret damage
Frets with flat crowns or deep grooves change the string length and throw off intonation. Frets can be repaired or replaced if necessary. I can not detect any fret ware on my 3rd fret.

Fret height
A tall fret can play incredibly sharp if you press hard on the string. Test different pressures while using a tuner. With my bad G note, the lightest possible pressure puts me at 12 cents off, and the most pressure puts me at 25 cents off. By comparison, for the A string, my light to medium pressure gives a dead on C note, the strongest pressure puts me sharp by only 5 cents.

Poor Quality / Defective / Worn Strings
Cheap worn strings can cause intonation issues. I'll try some new quality strings today to see if that helps, but there is no visual defect in my current low E string.

Fret Layout/Spacing
This is rare, but happens on inexpensive imported instruments or with a fretboard that was slotted by hand. If the angle of the fret was wrong, I'd expect my fretted C note on the A string to be off, but it isn't.

Summary: Bad bridge adjustment, high action, barely noticible fret ware on the 3rd fret and possibly a worn out string is causing my G note to be annoyingly sharp on my Martin acoustic.

Quiz: The bridge plate is pulling off the body about 1 mm. If it was flush and the string length was 1 mm longer, would this make my bridge position problem better or worse?