deja vu
I guess this topic has to come up and get the living hell beaten out of it at least once a year for good measure, so why not...
46'bird: do you really notice shifts in intonation between sets of strings of the same type, or do you just do it as a confirmation check (to sleep better)? I didn't think the slight differences in string gauge tolerance would be measureable.
As for the fretted note vs harmonic test, fret placement is imperfect, and it is the primary reason why intonation must be set in the first place. But a 12th fret harmonic, on the other hand, does not change pitch by moving your
fat finger around a little, and is always loudest at the midway point along the string. An argument can therefore be made that intonation must always be set against fretted notes, not harmonics (unless of course you always play harmonics instead!).
But why stop there, at the 12th fret? What if your guitar manufacturer positioned the 12th fret slighty off of dead-center by a few thousandths of an inch (after all, it can never be perfect), and say for argument's sake that most of the other frets happen to be better positioned, closer to where they should be after being hammered into the slots in the fretboard. In this case you are worse off setting intonation using only the 12th fret than if you did a balancing act among all frets. It's always a trade-off. The open / 12th fret check is just a quick and dirty check.
I should mention here that a couple of years back I was puzzled over why some of the lower notes along my G-string always seemed a few cents sharp, particularly the A note at 2nd fret which may be one of the most popular spots on the fretboard. After lots of theorizing with folks on this forum, including GT the instigator for this post, it turned out to be improper string height at the nut. That string was slightly higher than its neighbors - that's all it took. I had a guitarsmith file things down evenly (what they call "regulating the nut"), and there went my intonation problem.
Someone on this forum turned me onto an incredibly accurate computer-based shareware tuner called TuneLab 97. For anyone interested...
http://www.tunelab-world.com/
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