After a long time fattening up our piggy bank, we've managed to save the money we need to buy a new guitar or bass. We have several options in mind and we're swimming in a sea of doubts, because we want to make the right purchase. The most popular criterion when choosing an instrument, though not the wisest, is price—"if it's expensive, it's good"—and even better if one of the musicians we admire plays it. In this article I'll try to provide more arguments and ideas for evaluating a guitar or bass so that your choice is as sound as possible. To do so, I'll draw on statements and ideas from builders and musicians, as well as on my own experiences, which have allowed me to confirm that they are correct.

In the past, most people considered solid-body guitars to be an inert instrument whose acoustic properties depended mostly on the pickups and the amplifier. People added brass nuts and bridges based on the "if it's heavy, it sounds good" theory, as well as preamps and boosters.

In the '80s this trend changed, and people began to recognize the acoustic properties of the solid-body electric guitar and that these are the real source of its sound quality/tone. What was really being done was using electronics to amplify the small acoustic "output" of a solid body, which together with the neck, bridge and nut forms a resonant unit with a characteristic voice, depending on the materials used and the type of construction. The pickups reproduce that voice and, depending on their characteristics and those of the other electronic components, in turn add a certain "color" to the instrument's voice.

How the choice of all these components affects a guitar's final tone is a subject that still sparks all kinds of opinions today. Even though the electric guitar has been with us for quite a few years and was created in the 20th century—a century in which science made materials testing and measurement methods available to every kind of industry—it seems that the age-old method of trial and error, along with the ear and intuition, are what builders use most. In fact, if we look at most electric guitar concepts, we'll see that practically all of them are based on the original ideas of Fender and Gibson.

Next we'll go through all the parts of the guitar one by one, discussing the particular characteristics of the materials used to build them.

The body
In an electric guitar, the body acts as the soundboard, so the choice of wood will largely determine the final result as far as tone is concerned, since depending on the type chosen it will reproduce the vibration of the strings in one way or another. And although there can be differences between pieces cut from the same tree, due to factors such as weight and density, general statements can be made for each type of wood. In issue 97 of this magazine you'll find an article covering the particular characteristics of each type of wood; nevertheless, I'll briefly review them.

Maple: Besides its use for necks, it is often used in body construction, as a top, in combination with other woods, because of its bright, percussive tone and its ability to produce a strong fundamental response without much coloration from upper harmonics.

Mahogany: Warm, round sound, rich in harmonics and with long sustain.

Swamp ash: A lightweight wood whose main characteristic is a transparent, "bell-like" sound that works very well with single-coil pickups.

Alder: A wood that adapts well to all kinds of styles because of its ability to reproduce both lows and highs with definition.

These are the most popular woods, but others such as basswood, walnut, birch, zebrawood, bubinga, etc., as well as synthetic materials, are also used with greater or lesser success.

Some builders make solid bodies with resonance chambers, which, besides reducing weight, help increase bass response and warmth; sustain is also increased, even at moderate amplified volume levels.

The neck/body joint
The way the neck is attached to the body is one of the determining factors in a guitar's final tone, since the vibration of the strings travels through the neck and into the body through the joint between them. On bolt-on neck guitars, a good joint is critical, and this is a point on which professionals from the Fender and Ibanez Custom Shops, as well as renowned independent builders, agree. For a bolt-on guitar to sound its best, the neck must fit as snugly as possible and make contact on all sides of the joint, and if we also keep the amount of finish or lacquer in the joint to a minimum, we'll be helping to improve the guitar's tone. This type of construction makes some frequencies stand out over others, which is known as "twang," since attaching the neck with screws instead of glue distributes forces and tensions differently.

Neck-through guitars are those in which, as the name indicates, the neck runs from end to end, that is, from the headstock to the strap button; to build the body, two pieces of wood are added on either side of the neck. Generally the wood used for the neck, which is also the central part of the body, is maple, so the characteristic timbre of this wood predominates, since the pieces added to create the body can't exert the influence a complete separate body would. Nevertheless, different types of wood can be combined to achieve greater warmth as well as better low-frequency response.

Set-neck guitars, such as the Gibson LP, replace the screws with glue, and many builders claim this adds a more "singing" character to the sound, as the notes seem to swell after the pick attack until they reach full amplitude. Sustain, warmth and moderate attack are the characteristics attributed to this type of guitar.

In practically every neck there is a hidden component that plays a decisive role in the guitar's tone: the truss rod. The truss rod's function is to counteract string tension and allow the neck's curvature to be controlled, but it alters the neck's mass and torsional rigidity.

The truss rod should always be under tension, since if it is completely loose it could vibrate sympathetically along with the strings, absorb certain frequencies and reduce sustain.

The most common truss rod designs are double and single. Double rods favor sustain and definition, due to their greater weight and rigidity, while single rods usually have the opposite effect, helping to achieve warmer tones.

The headstock
The type of headstock is another determining factor in the sound. There are straight ones (Fender) and angled ones (Gibson). Flat headstocks are basically a continuation of the neck itself; the wood grain runs from end to end without any interruption, and the strings exert less pressure on the nut, producing a livelier, more open sound. Necks with angled headstocks can be of two types: one-piece neck and headstock, or with a glued-on headstock. Most builders and musicians believe that with a glued-on headstock some of the essence of the neck wood is lost, since the final sound is influenced by the added piece and the glue used for the joint. On this type of headstock the strings exert more pressure on the nut, which helps increase sustain, since more energy is transferred to the body instead of dissipating through the headstock.

Tuners
By changing a guitar's tuners we can alter the neck's resonant frequency, which changes the instrument's tone; sometimes the change is positive, but sometimes it isn't. Where it's most noticeable is on guitars with bolt-on necks and straight headstocks; generally, when we add heavier tuners to this type of neck, there's usually a noticeable improvement in sustain and tone. We should pay close attention to this aspect only if we find that, after changing the tuners, we've lost some of the instrument's desired tonal characteristics, since it isn't one of the main factors in the final tone. The main thing with tuners is that they be a solid unit with no play between their parts, to avoid vibration and noise problems and to ensure tuning stability; it's also desirable that they have a smooth, precise action when tuning.

The nut
Years ago, many guitarists and bassists replaced their plastic or bone nuts with brass ones, believing this would improve the instrument's overall sustain. But as many luthiers point out, the nut can only directly influence the sound of open strings, since once we fret a string at a given fret, that fret automatically becomes the nut. For my part, I partially agree with this statement, since I believe the type of material does affect the sound, albeit very subtly. The key thing is that the nut be perfectly installed, making contact with the neck as precisely as possible, since a nut that doesn't seat properly can dampen string vibration, changing the response and causing some frequencies to be lost. That's why it isn't advisable to use the popular home method of shimming nuts with bits of paper to adjust their height. The slots where the strings sit must be the right size for the gauge you're going to use, since if the strings are too loose, vibration noises and loss of tone can appear when playing open strings.

The fingerboard
The fingerboard is one of the elements that helps shape a guitar's final sound.

Depending on the material, it "filters" the vibration of the strings differently, altering the instrument's tone. Fingerboards can be wood or synthetic. The most popular woods are ebony, maple and rosewood; synthetic materials include graphite and various plastic and fiber composites.

Ebony is the hardest and heaviest of the woods used for fingerboards; it usually provides a fast-responding sound with definition, clarity and quick decay, making it an ideal choice for anyone who does a lot of legato and tapping.

Maple doesn't respond as quickly as ebony; it produces a more balanced sound, with brightness and sustain. It's highly recommended for bassists who play a lot of slap, and for guitarists, depending on the electronics and body wood, it can suit a variety of styles, from metal to country.

Rosewood fingerboards have a warmer sound with a less defined attack; the sound seems to swell just after the string is played. These qualities are usually attributed to the wood's high oil content, which dampens high frequencies and makes the midrange stand out.

In upcoming installments we'll look at how the frets, bridge, electronics and finishes affect tone; how to evaluate and improve an instrument; and some basic tips for keeping our guitar or bass in top shape.

Until the next installment, friends.