Question re: intonation

[StringFive]

I understand that if the intonation is out of whack a guitar will play more and more out of tune as you play notes and chords up the neck....generally going sharp. But is the opposite also true? I've never heard of intonation going flat. Is that something that happens as well?

[Howard Emerson]

Originally Posted by StringFive

I understand that if the intonation is out of whack a guitar will play more and more out of tune as you play notes and chords up the neck....generally going sharp. But is the opposite also true? I've never heard of intonation going flat. Is that something that happens as well?

All the time.

The older strings get, the flatter they will tend to intonate.

Also as frets get grooves worn in them, the string will play off the back edge of the groove (the nut side of the fret) and they will play flat because of that.

Most of the time 'going sharp' has more to do with operator error than it does with the instrument, due to grip of death.

HE
It Ain't Necessarily So: http://howardemerson.com/music2.html

[Alan Carruth]

Howard Emerson wrote:
"Most of the time 'going sharp' has more to do with operator error than it does with the instrument, due to grip of death."

As Scotty said:"Ye canna br-reak the laws o' physics, Capt'n!" Pressing the strings down on the frets raises the tension, and the added tension causes them to go sharp in pitch. How much a given string goes sharp depends on a lot of factors, such as the nature of the string itself, the action height, how much relief there is in the fretboard, and how hard you press it down. Usually, if the setup is reasonable, there will be some combination of nut and saddle compensation that can get the intonation acceptably close to 'right' for a given set of strings and player. Another player, who uses more or less pressure on the frets, might find the intonation to be further off than they like.

Be aware, too, that it's impossible to get the intonation 'perfect' for every note on every string on any acoustic guitar, using straight frets, if only because the top moves. Even if you could, it would still be equal temperament, which many people with good ears find to be problematic at best. In the end, tuning, temperament, and intonation are compromises.