Guitar Scale Theory: Simple Explanation and Illustration

Many guitar players don't fully grasp, or understand the concepts behind the notes they play. It's not that a guitar player needs to know a lot of music theory; rather they need to know just enough to help give meaning and connectedness to fretboard movement.

The right kind of music theory gives us a better handle on the mechanics of what we play and why we play it.

In my attempt to offer a more full explanation of the term "guitar scales", I'll use enough theory to deliver the concept, while avoiding information that doesn't benefit you directly in your understanding of the fretboard.

Knowing a Little Theory

To be honest, I've been in the same boat regarding some of these concepts. I've got a good ear, but I'm not much for the technical aspects, and I think that's how most guitarists are, if they're honest.

Unfortunately we're doing ourselves a disservice if we don't at least understand the basic theoretical concepts behind what we're doing on the fretboard.

We'll avoid paragraphs of confusing text and present guitar scale theory in the most straightforward and easy to understand method possible.

Short paragraphs and some pictures.

What is a Scale?

The most basic explanation of a guitar scale would be the following:

Guitar Scales
A group of notes on the guitar arranged in ascending or descending order.

Now obviously there's more to the story, but it's less scary once you realize that in its most basic form, a scale is little more than a collection of notes that either follow each other higher, or lower.

Whole Steps and Half Steps

Once you understand that your scales are a collection of notes, you need to know how to identify those notes and the movement between them.

It's likely that you already understand the concept of musical letter notes, which are made up of the first seven letters of the alphabet: A B C D E F G.

These seven letters are how musical notes are represented, thus each individual note on the scale will have one of these letters associated with it.

It's when you begin to move between these notes that you're being introduced to a new concept: Changing pitch, which is measured in half and whole steps.

Half Steps -- If you start with your first finger on the 1st fret of the sixth string (low E), then move your finger up to the 2nd fret on the same string, you've moved up in pitch 1/2 step.

Whole Steps -- If you start with your first finger on the 1st fret of the sixth string (low E), then move your finger up to the 3rd fret on the same string, you've moved up in pitch 1 whole step.

Guitar Scales Guitar Scale Theory

It's the same concept as tuning down 1/2 or a whole step, which is a term you've probably heard before. If you didn't know what it meant before, you do now.

These terms give us a way to describe movement up and down the fretboard, particularly when we're talking about ascending or descending scales.

Scales typically will have a mixed arrangement of half steps and whole steps. Consider the following basic scale diagram.

Guitar Scales

I've circled two half steps and one whole step. Whenever they show up in scales, this is all you need to know; that they come in one and two fret jumps.

If it's a three fret jump, say the 1st to the 4th fret, we'd call that "one and a half steps", or if it went from the 1st to the 5th fret we'd say, "two whole steps".

Scales and "Keys"

When you hear the term "key", you probably think of a phrase like, "This song is in the key of E", or something like that.

Keep doing that, but also realize that scales are where those keys actually come from.

Let's talk about the relationship.

What is the link between songs, scales and keys?

We can know right away that our "key" is going to be one of the seven musical notes, which we attribute to songs we play.

However we need to keep in mind that scales actually are right in the middle of our songs and the key it's being played in. Our songs are based off of a scale, which has a key.

In guitar terms if we were to move the scale up or down the fretboard, the key would change.

Therefore the more correct explanation is that our songs have scales, which have keys.

Guitar Scales

Scales take their name from the first note played in their note order, or the "root" note of the scale. This letter name gives them their key.

Once you know what kind of scale you're playing and in what key, you can move the scale or any segment of it to any location on the fretboard, thereby changing its key.
Guitar Scales

As the scale or segment of a scale moves, so does the key. Once you understand this, you'll start to have a better understanding of why certain notes work in certain scales and others don't.

In the long run, it will help you improvise.

Complete Chromatic Scale

Western music uses 12 notes, which can be referred to as "The Complete Chromatic Scale". On a keyboard or piano, this is represented by seven white keys and five black keys.

On a guitar, this is represented by 12 frets.

The chromatic scale on the guitar can be visualized by going from the open E on the sixth string to the 12th fret (high E) on the same string.

Those 12 notes make up the complete chromatic scale on the guitar.

Guitar Scales
All the guitars scales you will ever see in your life are derived from this simple 12-note system. All the different sounds, varieties and arrangements we get come from a variation of this sequence.

Delving into the A Minor Pentatonic Scale.

Though the primary intention of this article is to cover the theory and technical aspects of guitar scales, we'll delve into some basic application here using the A Minor Pentatonic Scale.

This scale is the most popular, particularly for guitar players, in western music.

What we'll do is cover the full 12-fret model of the scale, then break it down into smaller chunks. Keep in mind that any chunk can move to any fret.

Guitar Scales
A Minor Pentatonic Scale -- 12 Frets

The small blue circle on certain red dots. signifies the root note at different octaves (which in this case is A).

What we want to do now is break the scale down into smaller more useable chunks, which can then be memorized and transposed to anywhere on the fretboard.

We'll start with the first few frets.

First Segment


First first segment of the scale deals exclusively within the first three frets and the first four strings of the guitar. This scale or "mode" should be handled in three different steps during practice:

  1. Memorize the pattern as it is.

  2. Memorize the sound.

  3. Transpose the scale to another fret.

Let's say for example, that you wanted to move the pattern up to the 5th fret. The tab would then look like this:


You're still jumping up one and a half steps for the two lower strings, and one whole step for the two higher strings. However the mode takes on a new key as a result of moving frets.

The key of the scale starting at the 5th fret is D.

Second Segment


Since we've already covered the process of transposing to another fret, I won't rehash that here. However the same practicing goals apply.

Third Segment


The process repeats for the third segment.


Understanding the musical concepts surrounding the guitar is tricky, since in-depth, complex music theory isn't required to be a good guitarist. Yet we need to know enough to know why we play what we play and what all the movement on the fretboard actually means.

Scales are a good place to start and if you have a general knowledge about how they work, you'll be able to apply that knowledge to almost all other areas of your playing.

Feel free to post comments and questions below! Thanks for reading.

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About Robert Kittleberger
