Intonation drift

The gradual loss of accurate intonation as the instrument changes with temperature, humidity and time, so notes that were in tune start sounding sharp or flat.

Wood absorbs and releases moisture, which alters the neck's relief and the string's speaking length slightly, and temperature changes string tension. Players notice it as chords that were fine at rehearsal sounding sour at the gig, particularly on the higher frets. It is usually answered by checking relief and adjusting the saddle positions, though in a swing of extremes the tuning of the instrument itself will also have moved.

Example: a guitar set up in a warm studio will often play sharp in a cold van and need a few minutes to settle before a soundcheck.

Intonation drift

See also