Anatomy of an Acoustic Guitar

Headstock

Tuning Machines / Machine Heads

Nut

Neck

The guitar’s neck is home for the headstock, tuning machines, fingerboard (fretboard) and strings.

Necks are either fixed using glue (set neck) or bolted directly on to the body. In the case of acoustic and classical guitars, this is almost always glued in place.

The longer the neck, the longer the guitar’s scale length (the distance between the saddle and nut). Generally speaking, the shorter the scale length the ‘warmer’ the tone, whereas the longer the scale length the brighter the tone.

The wider the neck, the more area the fretboard utilises. Generally guitars manufactured to be played with the fingers e.g. classical and finger style guitars feature a wider neck to provide more space between the string making it easier to play individual strings. Most steel string acoustic guitars utilise a 43mm neck width, measured at the nut and commonly referred to as nut width. Classical guitars on the other hand will typically be over 50mm in width at the nut.

Necks also come in different depths (e.g. the thickness of the neck) and shapes (e.g. the roundness of the underside of the neck), known as neck profiles. (C, V, and U for example).

Frets and Fret wires

The frets of a guitar refer to the areas between the metal fret wires located on the fretboard, used to separate the guitar’s fretboard into semi-tone intervals.

Most guitars utilise 21 frets, however, some electric guitars have 24 frets.

Fret wires are shaped like a mushroom or ‘T’ with the top section sitting on the fretboard and the stem embedded into the fretboard. The top of the fret wire is rounded to aid playability and is referred to as the crown.

Fret wires come in a variety of sizes, from tall, short, skinny and wide. This chart shows most available fret wires for guitars and other stringed instruments.

Fret wires can wear over time, particularly if the guitar is used regularly. When this occurs, frets may need to be replaced or repaired. This is known as fret dressing which involves levelling and reshaping the top of the fret wire.

Fret Markers / Inlays

Fret Markers (also referred to as inlays or positional markers) are located on the guitar’s fretboard and indicate specific frets of the guitar’s neck. This allows the guitarist to orientate the guitar’s neck.

Typically guitar inlays will be found inset onto the 3rd, 5th, 7th, 9th, 12th, 15th, 17, 19, and 21st frets.

Inlays are seen in a variety of shapes, however, most typically are either square, trapezoid, or dots. In the case of dots, the 12th fret of the guitar usually contains two dots to indicate the octave. Inlays are made from a variety of materials including, plastic, mother of pearl and abalone to name just a few. Inlays are usually not seen on classical guitars, which typically only feature fretboard side dots.

Fretboard side dots are dots found on the side of the guitar fretboard at the same locations on the neck e.g. 3rd, 5th, 7th, 9th, 12th, 15th, 17, 19, and 21st frets.

Truss Rod

The truss rod is the metal tensioning bar running through the centre of the guitar’s neck that can be adjusted to modify the amount of relief or bow in the guitar’s neck. The image to the left shows a cross section image of the guitar neck, with truss rod running through the middle of the neck.

Generally speaking electric guitars and steel string acoustics will require a truss rod however many classical guitars do not due to less tension being applied to the neck due to less tension being applied to the neck when using nylon strings as opposed to steel strings.

Fretboard / Fingerboard

The fretboard (also referred to as the fingerboard) is the section of timber laminated onto the main area of the neck. It is usually manufactured from rosewood, ebony or maple (more commonly seen on electric guitar fretboards and necks).

Pressing the strings against the fretboard creates individual notes e.g. melody. Pressing multiple fingers against the fretboard at designated frets produces harmony or chords.

In the case of acoustic guitars, the fretboard has traditionally been rosewood. For high end classical guitars, the choice is often ebony. Rosewood is particularly popular as it is an oily timber, ideal for reducing tension between the fingers and fretboard and is credited with contributing to producing a warmer tone.

Heel / Neck Joint

The heel (also referred to as the neck joint) is the where the neck joins to the body of the guitar, along with the sides of the guitar body.

For acoustic guitars, in the majority of cases the neck will be glued, using a dovetail joint, a particularly effective type of joint commonly used on acoustic guitars.

Back and Sides

The back and sides of an acoustic guitar are usually paired. Rosewood, maple and mahogany are often paired with mahogany being an ideal timber due to being hard but workable.

The back and sides make up the stable elements of the body, with the soundboard or top wood responsible for vibrating and resonating sound.

Lower Bout, Waist and Upper Bout

Acoustic guitar bodies comprise of an upper bout, which is the top half of the guitar and a lower bout (the bottom half of the guitar). The bouts are separated by the waist, which is the narrow section located between the two bouts.

The shape and size of the body of an acoustic guitar influences the playability of the instrument with regard to how comfortable the guitar is to play. More importantly, the body shape and size influences the tone of the guitar as it affects the internal ‘air resonance’ of the guitar. For example, a wider lower bout lowers air resonance and gives more definition to the low end tonal output of the guitar.

* Tone is influenced by a number of contributing factors. Body shape is just one of these.

Sound Hole

As the name implies, the sound hole is the hole located on the guitar’s soundboard.

In the majority of acoustic guitars, this is simply a circular shape but variations known as F-Holes are also seen in some acoustic guitars (mainly jazz acoustic/electric guitars and electric guitars).

Gypsy guitars (Selmer guitars) tend to have an elongated sound hole, while some manufacturers such as Bourgeois and Martin feature select guitars with larger than normal sound holes.

Contrary to popular opinion the sound hole is not solely responsible for the guitar’s sound, this typically originates from the body of the guitar, in particular the soundboard, however, the sound hole opens up the body to allow greater resonance and facilitates the release of internal ‘air resonance’.

Rosette

The rosette refers to the decorative rings located around the sound hole.

While the rosette may appear to be decorative only, rosettes are actually used to reinforce the timber around the sound hole, which otherwise would be subject to cracking.

Pick guard / Scratch Plate

The pick guard (also referred to as the scratch plate) is located to the underside of the sound hole of the guitar body. As the name implies, the pick guard is used to ‘guard’ or protect the guitar’s body from the pick, that over time would otherwise scratch the guitar’s surface.

Pick guards are typically constructed from three separately laminated pieces of plastic (three-ply) and come in a variety of different shapes.

In the case of classical guitars, these are usually not used, as classical guitarists tend not to play with a pick. In the case of flamenco guitars however, the pick guard is replaced with a clear protective plate referred to as the golpeador that protects the guitar‘s soundboard from the more aggressive strumming patterns flamenco music incorporates.

Binding

Binding, refers to the strip (vinyl, PVC plastic, amongst other materials) that is seen on the seam between the top and sides of the guitar. It is also sometimes seen on the back of the guitar and the neck. If the neck features binding it is referred to as a bound neck.

Binding serves three purposes. firstly it provides a decorative element between the sides and soundboard. Secondly it protects the edges of the guitar which are most prone to impact and lastly it shields the open grains of the timber used for the soundboard preventing the absorption of moisture.

• Faux binding is when binding has been imitated using either the timber of the guitar‘s soundboard or paint.
• Purfling is similar to binding, however it is usually the thinner strip located on the inside of the binding usually consisting of a contrasting color.

Soundboard

The soundboard is an essential part of the guitar‘s anatomy and refers to the top of the guitar’s body, which houses the bridge and sound hole.

Acoustic guitars rely on resonance to project sound. The soundboard resonates due to the bridge being fixed to the soundboard which vibrates due to the guitar strings running directly over the saddle which is located in the middle of the bridge.

While the choice of timber is less critical on an electric guitar due to the additional components involved in creating tone, on acoustic guitars the choice of tonewood can play a major role in the guitar’s overall tone, resonance and ultimately volume.

The wood used is selected for its strength, and lightness. This is because the sound board must vibrate freely to produce sound but also handle the tension applied by the steel strings. Soundboards utilise bracing, to add additional tensile strength.

Bridge, Saddle And Fixing Pegs

The bridge is the part of the guitar that fixes the strings to the body and allows for the vibration from the strings to resonate through the body of the guitar, projecting sound.

Strings are typically fed through small holes in the bridge and locked in place by the bridge pins (also referred to as fixing pegs) which are pushed directly into the string holes, located on the bridge.

The bridge also features the guitar’s saddle, which is often made from the same material as the nut of the guitar.

Unlike the nut, however, the saddle is positioned on an angle with the end closest to the bridge pins reserved for the bass strings, allowing accurate intonation. Essentially the thicker strings e.g. ‘E’ and ‘A’ require slightly more length to compensate for their additional tension when fretted due to their wider surface area.

Bracing

Located on the underside of the guitar‘s soundboard and back is the bracing. Bracing refers to the wooden struts (structural components made from spruce, or a similar light yet strong timber) that reinforce the guitar‘s top and back.

Bracing supports these larger, lighter sections of timber structurally without adding much additional weight which would impact the guitars ability to resonate. Some struts are scalloped, which is a technique used to reduce the weight of the struts further while maintaining structural integrity.

There are many different types of bracing, including X bracing which is the most common form of bracing amongst steel string guitars. Classical guitars commonly utilise fan bracing.

Most guitar backs utilise ladder bracing, a simple form of bracing where the struts are fixed to a centre strut and run perpendicular to the strings in much the same was as a ladder.

Summary

The components of the guitar referred to above are found on the majority of acoustic guitars. There are, in many cases differences between manufacturers particularly in regard to the headstock shape, tuning pegs, fretboard timber, fretboard wire gauge, rosette style and material, inlay material, bridge design and material and of course the tone woods selected for the construction of the guitar. However for the most part the basic anatomy will be similar across different models.

All of these differences account for the range of tones extracted from different acoustic guitars and the music they are most suitable for playing. This is just one of the reasons why owning one guitar is never enough.

Enjoy the article? Got a question about the anatomy of your guitar? We’d love to hear from you in the comment section below.

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Marty

My names Marty, I've been into guitars for over 30 years. Theacousticguitarist.com is my blog where I write about acoustic guitars, music, and home recording.

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