How Acoustic Guitars Work 101

This page covers some basic information about how acoustic guitars work and function to help you make music.

Acoustic guitars play notes that are audible in the open air without amplification, by a vibrating string that resonates inside the hollow wooden body of the guitar. Depending on which fret and string is pressed, you can have a varying range of pitches. As vibrations travel through the saddle and bridge to the interior of the guitar, the hollow body naturally amplifies the sound, making it louder in open air.

Parts of the Acoustic Guitar: Body, Neck, and Head

A full explanation of an acoustic guitar's functionality is a little more complex and nuanced. Let's start by addressing the three major parts of the acoustic guitar, what they're for, and how they work.

We'll go through all three parts - body, neck, and head - one at a time.

How the Body Work and Picking/Strumming the Strings

An acoustic guitar's body will have the most say about what that guitar sounds like. More specifically the top of the guitar is the most crucial part, since that's where the bridge connects the strings to the body. This is why many acoustic guitar manufacturers will put more money into the top, because it'll make the guitar sound nicer. This often means solid wood is used for that top piece, while laminate is used for the back and sides.

The body of the guitar works via the soundboard which contains the sound hole. Attached to the soundboard is the bridge where the strings are attached and rest on a small piece called the saddle. When the strings vibrate, sound is carried through the saddle, through the bridge, and into the soundboard, which projects inside the body of the guitar and resonates outward.

Here's a horizontal view of how the saddle, bridge, and soundboard fit together. You can see they are all connected below the strings:

From this graphic, it's easy to see how sound could travel down through the parts of the guitar and resonate inside the acoustic's hollow interior. In this scenario its the hollow body itself that serves the role of amplifier and projects the sound.

Looking at the body from the top view again, the shape is intentional. The narrowing in the middle, sometimes called a "waist", is designed to rest on your leg and make room for your strumming arm. The wider portion where the bridge connects is called the lower bout while the wider portion where the neck connects is called the upper bout.

How the Neck Works and Pressing (fretting) the Strings

An acoustic guitar's neck is the long, flattened portion that is attached to the upper bout. The neck contains the fretboard which is usually a separate, implanted piece of wood with each fret separated by a small piece of smooth metal.

Read more: Acoustic guitars with wide necks

In order to change the tension of the strings, an acoustic guitar player will press a particular string on one of those frets. This change in tension will change the pitch of the string, thus changing the note. The further up the fretboard you go (towards the guitar's body) the higher the pitch of a given string will be.

This is why each string has its own set of notes for each fret, given a specific tuning. 

For example, if you tune an acoustic guitar to standard tuning, the sixth string played at the fifth fret is an A. The seventh fret is B, the 10th fret is a D and so on.

While the body handles tone and projection, the fretboard is where the acoustic guitar player does his or her work to alter pitch by pressing the string down on specific frets.

Head or Headstock and Tuning Machines

Acoustic guitars also have what's called a head or "headstock." The primary function of this piece is to tune the guitar and serve as an attachment point for the strings. Tuning the acoustic guitar allows you to set a default pitch for each string or what I referred to earlier as a "tuning." For most acoustic guitar players, a standard tuning is most common.

Each tuning peg can be turned to either tighten or loosen tension. Keep in mind, while this is a part of how acoustic guitars work, it's not a mechanism that's necessarily unique to acoustic guitars. Most stringed instruments are tuned in a similar fashion, with a headstock and tuning pegs of some kind.

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