A set up consists primarily of adjustments to the following

The purpose of a set up to allow the guitarist the greatest possible degree of ease in playing the instrument. We've all probably had the experience of having to fight a guitar that has not been well set up, sometimes without having any real idea of why it feels so hard to play.

This list is only the main points; there are often many other minor adjustments specific to different models which address things such as bridge balance and tuning machine stability.

Nut height: A nut which is too high will make the guitar difficult to play; the action will feel stiff, particularly in the first quarter of the fingerboard. the increased stretching of the strings will also cause the guitar to sound out of tune and it will be almost impossible to get the action low by adjusting the bridge and saddle height.

Nut slot profile: If the slot profile is wrong the string may stick and jam, causing tuning and stability problems. Too wide a slot, or a flare on the slot's profile may cause an odd, muted buzz.

Truss Rod: This controls the string's arc relief, which is the shallow curve in the neck which allows the string room to vibrate. This is critical to achieving low action with minimal string buzz but can be compromised by the condition of the frets. Most guitars are set with far too much arc relief; getting this right can make all the difference between a good set up and a bad one.

Saddle height: The saddle height is probably the least important element in the set up yet it is usually the first adjustment that the inexperienced goes for.

Saddle position: The gap between string and fret results in a slight stretching of the string, raising the pitch. This is compensated for by moving the saddle, lengthening the sounding length of the string slightly and lowering the pitch by an equivalent amount.

All the set ups that I do include a process of tempering intonation by ear which produces a more accurate perception of intonation than is achievable by using digital meters.

Find out When and why you shouldn't use digital tuners

Pickup height: a poorly adjusted pickup can affect string performance and intonation. Proximity to the strings can also be used to control both output and tone.

Why do I need it?

Because larger manufacturers can't devote the time and resources to to refining the set up of every one of the thousands of guitars they produce every month, still less can they second-guess the individual requirements of every player who might buy their product, for optimum performance a set up is mandated on pretty much every new guitar.

This is where the skill of the guitar technician comes in to play.