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Acoustic Guitars - The Basics
The acoustic guitar is a familiar sight to us all, but if you are just starting out on your guitar playing journey there are some basic pieces of knowledge that you need to learn to make the relationship with your guitar an easier and more enjoyable one right from the beginning. Turn your guitar to face you with its bottom on the floor and its neck pointing at the ceiling. We'll start from the top...
Headstock - The flat extension at the top of the neck is called the "headstock", "peghead" or simply the "head". The purpose of the headstock is to locate the tuning mechanisms for the instrument (see Tuners below). Another function of the headstock is to provide string tension over the nut (see Nut below). To create this tension the headstock is splayed backwards slightly, away from the strings. This makes the joint between the head and the neck particularly vulnerable to impact damage, so always take care when playing or handling the instrument to avoid knocking the headstock. The headstock usually allows access to the truss rod (see Truss Rod below), the access hole for which is often concealed under a triangular plate on the headstock.
Tuners - Most Western acoustic guitars have individual covered or sealed tuners which are sometimes called "machine heads". When the tuning knob is twisted the motion is exaggerated via a worm-gear mechanism which turns a capstan on the face of the headstock to which the appropriate string is attached. This increases or decreases the tension on the string causing it to increase or decrease in pitch when played. Some older or cheaper models may have exposed gearing with three tuners located on a single mounting plate.
Spanish, Flamenco and Classical acoustic guitars usually have two slots cut in the headstock across which the capstans rest. The tuners are then mounted on the edge of the headstock rather than the back.Nut - The nut is the slotted string guide to be found between the headstock and the neck, normally made from white, cream or black plastic but sometimes made from metal, bone or even ivory. The function of the nut is crucial to the quality and playability of the finished instrument. The nut represents the top limit of the strings' available vibrating length, it sets the string spacing for the instrument and greatly affects the action, that is the height of the strings above the fretboard (see Fretboard below).
Some guitars have a "zero-fret" (see Frets below), in which case the nut simply provides string spacing and tension over the zero-fret which itself sets the action and length of the string.Neck - The neck together with the fretboard will largely dictate the playing relationship you have with the instrument as it is here that most of the fiddly, creative stuff gets done. The neck of an acoustic guitar is generally of a more robust construction than that of an electric guitar because the acoustic guitar requires heavier gauge strings to create volume and tone without the help of amplifiers and speakers. The acoustic guitar also has a shorter playable neck-length than an electric. The acoustic neck joins the body via a heel that extends for the whole depth of the body. This heel is dovetailed into a block of wood that sits inside the guitar called the "top block" to ensure strength and stability against the pull of the strings.
Truss Rod - The neck is further stabilised by the addition of a truss rod. This takes the form of a rod of metal that is set into the neck before the fretboard is applied. In most modern guitars this is adjustable using the correct tool from the headstock end (how to make these adjustments will be covered in another article).
Fretboard - The fretboard, sometimes know as the "fingerboard" is glued onto the flat surface on the front of the neck and presents the guitarist with the playing surface. Traditionally fretboards are made from rosewood or ebony. At the head end the fretboard abuts against the nut (in some cases the nut is set in a slot cut in the fretboard). At the body end the fretboard extends beyond the heel of the neck onto the surface of the body ending at or just before the soundhole. This gives the maximum playable length (although access to the soundhole end is restricted by the bulk of the body).
Frets - In Western music only certain tones and musical intervals are considered pleasing. We call these tones "notes" and all our music is based for the most part upon scales made up from these notes. Frets are strips of wire set horizontally in the fretboard at the correct intervals to produce these notes. The player presses a string down onto the playing surface of the fretboard slightly behind the desired fret (never press down onto the fret itself). This causes the string to be stopped by the fretwire. Once the string is played by the other hand, the fret determines the length of the string allowed to vibrate which in turn dictates the tone or note that the string produces. This can be altered subtly for effect by the player bending the string along the fret or adding vibrato with the fretting finger.
Frets are set in slots in the fretboard and usually present a rounded polished profile to the player. The ends of the fretwire are carefully finished to prevent snagging.Fret Markers - To make it easier for the player to judge their position when moving about the fretboard most guitars have markers. The traditional dot markers are placed in the centre of the fretboard at the 3rd, 5th, 7th, 9th, 15th and 17th fret with a pair of dots identifying the octave at the 12th fret. There are many variations on the shape of marker, but they are always on the same frets. Even when no markers are visible on the face of the fretboard it is customary to retain them on the top binding of the neck where they are clearly visible to the player.
Body - Because the acoustic guitar has to produce its own sound it requires a sound-box to amplify the vibration of the strings. This is the case with all acoustic instruments and the size of the sound-box reflects the frequency response that the instrument is required to produce. A double bass needs to target low frequencies so the sound-box is large. A violin needs to reproduce higher frequencies so the sound-box is small enough to fit under your chin. So the size of the sound-box on an acoustic guitar dictates the volume and frequency response it is likely to give, from the deep booming voice of the biggest dreadnought to the staccato mids and highs of a Flameco or classical guitar.
Other factors affecting the sound of the acoustic guitar will be the woods and materials used in construction and how much the natural resonance of those woods is damped by the internal strutting and bracing necessary to keep the guitar together in one piece. The most important part of the body is the top, called the soundboard. This is generally made from the choicest material, the vibration of which does most to mould the voice of the guitar.Soundhole - The soundhole is situated in the soundboard, traditionally under the strings, and allows the vibration of the strings, amplified by the sound-box to be projected out to the listener. It's a sad truth that the player of an acoustic guitar, seated as he is behind the instrument, does not get to hear the true tone of his own playing (except via recorded play-back). The area of the soundhole is critical to the sonic performance of the guitar. The soundhole is often decorated by a rosette, sometimes in an elaborate way. Overly elaborate rosettes run the risk of affecting the vibration of the soundboard.
Pickguard - The pickguard is sometimes called the "scratchplate" and is attached to the soundboard directly below the soundhole. The purpose of the pickguard is to protect the finish on the soundboard from scratches caused by the players pick or "plectrum". Traditionally these are called "teardrop" pickguards as they look like a teardrop being squeezed from the "eye" of the soundhole. They are generally made from very thin material to minimise the effect on soundboard vibration, indeed some higher-end models dispense with pickguards altogether.
Bridge - The bridge is responsible for transferring the vibrations of the strings to the soundboard and thus the sound-box. Most acoustics have a fixed bridge which is a strip of high-density wood of a decent thickness. This is usually mirrored inside the sound-box by a similar piece. Preferred tone-woods for the bridge are rosewood or mahogany, on the best guitars the best tone-wood is used, ebony. The "footprint" of the bridge usually extends outside the width of the strings by a few centimetres each side to enhance the transference of string vibration.
Saddle - The saddle sits in a slot in the bridge and supports the strings, transferring their energy into the bridge and onto the soundboard. Bone and ivory are considered the best materials for the job, but in modern times acoustic guitar saddles are nearly always plastic. Like the nut, the saddle sets the length of the string and dictates the action. The saddle will normally have a small indent to accept each string which prevents sideways movement when playing. It will be necessary for the saddle to mirror any curve present in the profile of the fretboard.
The saddle also sets the intonation of the instrument. Each string needs to play in tune right the way up the fretboard. The differing gauge (thickness or heaviness) of each of the six strings means that the saddle always slopes to allow the 6th (thickest and heaviest) string a greater length than the 1st (thinnest and lightest) string. Some saddles allow for an extra "stagger" at the 2nd and 3rd string to further increase intonation accuracy.Bridge Pins - Traditionally each string is attached to the bridge by its own bridge pin. Six holes are drilled through the bridge and soundboard to the rear of the saddle. These are fitted with six tight-fitting plastic pins that have a slot cut into their shaft. Using a special tool (or a medium flat-headed screwdriver covered with a rag to protect your guitar) the bridge-pin is eased out after the string it holds in place has been completely de-tuned (loosened using the tuner or machine-head). The ball-end of the new string is the placed in the vacant hole, the bridge pin replaced firmly (not forcibly) and the guitar retuned.
Some acoustic guitars have dispensed with bridge pins entirely in favour of "slotted" bridges. On a slotted bridge there are holes drilled diagonally into the bridge through which the strings can pass but which will securely hold their ball-ends. In this way the bridge of the acoustic guitar mimicks the stop-tail arrangement common on electric guitars.
So now you know the anatomy of the Acoustic Guitar.
The Man in the Jar (The guitar world's equivalent of Dr Nick Riviera).
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