Intonation

The accuracy with which the fretted notes of a guitar match the intended pitches, set by the position of each string's saddle.

A guitar cannot be perfectly in tune everywhere at once, because fretting stretches the string and raises the pitch slightly. Compensation at the saddle corrects most of that error: the saddle is moved back so that the twelfth-fret harmonic and the fretted twelfth-fret note agree. The usual setup routine checks the fretted note against the open string and the twelfth-fret harmonic, and moves the saddle until they match, string by string.

Example: a guitar that plays in tune in open chords and badly out of tune at the twelfth fret simply needs its saddle positions adjusted.

Intonation

See also