There are many points I go over while inspecting and setting up a guitar, and one of the most important is the condition of the nut. Note how deep the strings are buried in this Epiphone Les Paul nut. When a guitar won’t stay in tune, very often the strings are binding at the nut or saddles in overly deep string grooves.
This Les Paul has had a hand-made bone nut installed. As part of a full setup, I re-shape and profile even a plastic nut to match this for better tuning stability and a more responsive, louder tone. With the top 1/3rd of the strings exposed at the nut, the strings don’t bind and aren’t muted by the nut sapping their sustain.
The neck is checked and adjusted for the desired straightness, which is a personal preference that makes a huge difference in feel. A very straight neck can add percussiveness, volume, and sustain by increasing string tension, while a neck with a bit of relief can be easier to bend without buzzing, add a bit more “fight” to the guitar, and round out the tone.
Every guitar will eventually need a fret dress, often even straight from the factory, but guitars with good frets still get tarnished by sweat and oxidation. A quick fret polish makes them play smoothly, removes grittiness, and makes sure notes ring out crisp and clear.
Several other critical adjustments happen on the body of the guitar. The pickups are set to their “sweet spot” for the best signal-to-noise ratio, even volume, and ideal tone– large differences come from small changes in pickup height, which can emphasize bass, treble, and overall timbre.
Additionally the bridge height is set for the desired string action– the guitar’s geometry must be balanced between the two anchor points, the nut and the bridge saddles, to feel perfect. The saddles are adjusted to match the radius of the guitar neck so each string feels even across the neck, and this setting can be adjusted slightly for personal feel. After all other adjustments are made, the guitar is intonated so that each string plays in tune all over the neck and octaves are in perfect harmony.
After a full setup the guitar should have a nice even action that is comfortable all the way to the end of the neck, the pickups should be balanced to sound their best, everything should be cleaned up, and you should feel like you’re holding a custom instrument tailored just to you. Get out there and play!