Guitar Theory: The 4 Step System For Rapid Progress

Want to learn guitar theory? In this lesson, we’ll show you everything you need to know about guitar theory.

guitar theory

In this free guitar lesson you will learn:

  • 5 must-know lessons which will turn you a guitar theory master.
  • 3 essential tips for understanding major and minor scales.
  • 2 top chord construction secrets.
  • 3 guitar theory hacks which will enhance your musicality.

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What Is Guitar Theory?

Guitar theory is essential to know if you want to become an advanced guitarist, guitar theory shows you HOW everything works in the guitar world.

There are 4 things you need to know about guitar theory, these are:

  • Guitar scales and intervals.
  • Chord construction.
  • Understanding musical keys.
  • How to use all of these elements in your playing!

Guitar theory can be a daunting prospect for many guitarists. However, it’s vital to know if you want to take your playing to the next level.

Guitar theory is a HUGE subject, so don’t expect to learn it all in one go. Take it one step at a time.

Put this lesson in your bookmarks and refer back to it as you progress in your theory journey.

Learning an instrument benefits your brain and body. Find out how in this article by The Guardian:Want to ‘train your brain’? Forget apps, learn a musical instrument

Guitar Scales

The first step in understanding guitar theory is learning guitar scales. A scale is a group of musical notes.

In music we have two types of scales, those are:

  • Major scales.
  • Minor scales.

Both scales are used to create different types of sounds, major scales have a ‘happy’ sound and minor scales have a ‘sad’ sound.

They both have their uses in all kinds of music.

In today’s lesson we’re going to talk about our scales in the key of ‘C’.

Want to learn about the key of ‘C’? Go here: Understanding the chords in the key of C

The Major Scale

The key of C has no sharps or flats. Therefore, if we’re playing in the key of C, that means the notes are:


Here’s a C major scale on guitar:

guitar theory

To learn this scale, go here: C Major Scale On Guitar

Because there are no sharps or flats, the key of ‘C’ is a nice and easy key to think in.

The Minor Scale

In music, we have relative scales. Relative scales, are scales in the same key which start off of different notes.

So for example, our C major scale contains the notes:


However, to create a minor scale in the key of C, we have to start off of a different root note.

That root note is ‘A‘, so our minor scale now has the notes:


Here’s the A minor scale on guitar:

guitar theory

To learn this scale, go here: Learn Guitar Scales In 8 Easy Steps

Can you see, how the scale has a different root note, yet it uses the EXACT same notes as the C major scale?

This is a classic example of a relative minor scale.

Download our lead guitar cheat-sheet to make things easier

It can be disorientating for guitarists to understand which scales work with which keys.

With this in mind, we created a cheat-sheet; a key and scale-finder that you can use again and again. Click here to download your copy.


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Each note in the scale has a relationship with the root note. These are know as ‘intervals’.

An interval is the gap between each note of the scale.

When we talk about intervals, we tend to talk about their relation to the root note.

This means, that if our root note is ‘C’, the rest of the notes in the scale have an individual relationship with the note C.

Like this:

guitar theory

We can apply a similar concept to the minor scale, however this time the minor scale has a different root note, so this means that the perspective of the intervals change.

Like this:

guitar theoryTry and use your instrument to understand guitar theory.

For example when you play your major or minor scale, you should:

  • Visualise what each interval looks like compared to the root note.
  • Listen to what each each interval sounds like compared to the root note.

When we learn a scale, it’s easy to find the root note and blast through the pattern without even thinking about what any of the notes are called.

Try this as a challenge:

  • Play the C major and A minor scales and name the notes as you play the scale.
  • Play the C major and A minor scales and name the intervals as you play the scale.

It’s important to understand this, as intervals and scales help us to construct chords.

guitar theory

Chord Construction

Understanding chord construction is really useful when understanding guitar theory.

This helps us to understand:

  • How chords are built harmonically.
  • Why certain notes of a chord work better with certain notes in a scale.

Guitar chords are built from each note in the scale. Here’s a really simple way to build chords off of scale. In today’s lesson, we’re going to apply this to the C major scale.


Pick your root note, this can be ANY note in the scale. However, for today’s lesson we’re going to use the note ‘C’.

guitar theory

After we’ve picked our root note, we skip across two notes to the 3rd note.

This means we now have the note ‘E’.

guitar theory

After this, we move across two notes again to the note ‘G’.

guitar theory

Therefore the notes in a C chord, are the note C, E and G.

The notes we have chosen are the 1st, 3rd and 5th note in chord. This is what’s known as a triad.

All major and minor chords, are created by using the 1st, 3rd and 5th notes. To change the chord, we just change the root note.

Like this:

guitar theory

You can build a chord off of each note in the scale. However, for each note in the scale, we get a different chord type.

So for notes:

  • 1, 4 and 5 we have major chords.
  • 2, 3 and 6 we have minor chords.
  • 7 we have a diminished chord.

This means in the key of C, notes 1, 4 and 5  are C, F and G. Therefore the chords are  C major, F major and G major.

The 2nd, 3rd and 6th notes are D, E and A. Therefore the chords are D minor, E minor and A minor.

The seventh note in a C major scale is B, so we have B diminished.

Now we understand how chords are built, lets take a look at how this works in a key.

Musical Keys

The definition of a musical key is often thrown around, this often means it can be difficult for guitarists to understand what they are.

Musical keys are a collection of notes that work well together. However, a musical key also contains chords.

We’ve already established that a C major scale has the following notes:


And that we can build chords off of those notes:

  1. C major.
  2. D minor.
  3. E minor.
  4. F major.
  5. G major.
  6. A minor.
  7. B diminished.

These notes and chords are what make up the key of ‘C’.

To learn more about guitar keys, go here: Guitar Keys: An Essential Guide

How Do I Find The Key of A Song?

99% of the time, you can tell the key of a song by:

Looking at the first and last chord of a progression.

Here’s an example:

From this we can tell this song is in the key of ‘A’. As the first and last chord are a ‘A’ chord.

What If The First Chord Isn’t The Key?

If you’re not sure on the key of a song, try playing a major scale over that chord progression.

If the scale is in the wrong key, you will know immediately. Experiment with a few different scales until you find one that fits.

Do Musical Keys Stay The Same In Music?

Musical keys change ALL the time. If everything was in the same key, music would become very boring very quickly!

Often, a song has a consistent key, however this can vary when songwriters borrow chords from other keys.

Usually to combat this, if we’re improvising or writing a melody, we would change our melodic notes to fit that particular chord.

However, don’t worry too much about this for now, just accept that it happens. The more you grow to learn about guitar theory, the more you’ll understand about key changes.

Now we understand what keys are, let’s take a look at how scales work in keys.

Scales That Work In The Key

As we found out earlier, the notes C, D, E, F, G, A and B are all notes which create the C major scale.

However, to play a scale in the key of C, we don’t actually need to play all of the notes.

A really great way to condense a scale down, is to play a pentatonic version of that scale.

If you wanted to play in the key of C, you could actually just play a C major pentatonic.

A C major scale, contains:


A C major pentatonic contains the notes:


Here’s a C major pentatonic:

guitar theory

Even though the pentatonic scale doesn’t sound as sophisticated as the full C major scale, it would still work over a chord progression in the key of C.

You could also do this with the relative minor scale, we’ve already discovered that A minor, was the relative minor of C major.

The notes in a A minor scale are:


The notes in the A minor pentatonic scale are:


Here’s the tab for a A minor pentatonic scale:

guitar theory

Learn this scale here: A Minor Pentatonic Scale: An Essential Guide

This means that, if you knew that a piece of music was in the key of C. You could use any of the following scales over it.

  • C Major Scale
  • C Major Pentatonic
  • A Minor Scale
  • A Minor Pentatonic

These all contains notes within the key of C, so they would all sound correct.

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How Do I Use Guitar Theory?

Picture the scene, you’ve spent hours and hours learning about guitar theory. But, you get to the band room and you just don’t know how to use it.

It’s great if you can learn guitar theory, however if you don’t know how and where to use it, knowing guitar theory is useless.

Here are 3 quick & easy ways to use guitar theory in a musical situation.

1) Guitar Theory Helps You Improvise Guitar Solos

Understanding guitar theory helps your solo skills. Understanding what guitar scales you can use over a chord progression is half the battle when improvising.

There’s nothing worse than struggling through a solo because you don’t understand understand the theory behind the music.

Knowing guitar theory puts a stop to your solo woes.

To learn how to solo, go here:

guitar theory


2) Guitar Theory Enhances Your Songwriting

Have you ever written a song?  Thought it sounded great, but it just needed that finishing touch. An extra chord? A key change to take the song to a new direction? A new melodic idea?

For example, lets say that you’ve written a chord progression which has the chords C and F, but it just needed something a little extra.

You could:

  • Add in an extra chord from the key of C to spice up the progression.
  • Use scales to create a new melody over the stop.
  • Change the key of a song.

Knowing guitar theory takes your songwriting to the next level.

3) Knowing Guitar Theory Enhances Your Musicality

Another great way of using guitar theory, is to add interest to chords and your own strumming patterns.

For example, let’s say we’re playing in the key of C, and the chords we’re using are C, Am and F.

As we know that the key of C, has no sharps or flats, we could actually use any of the open strings to add interest to these chords.

Learning guitar theory accelerates your progress as a guitar player.

However, we’ve only scratched the surface here. There’s a whole world of knowledge underneath the fretboard to discover.

Remember, guitar theory doesn’t turn you into a bad guitarist. It turns you into an excellent one.

Find Out What You Should Learn Next With Our Guitar Map

If you want to understand where you’re up to in your guitar journey you should take a look at our Guitar Map. It will show you what you ‘should’ know by now (and also what you need to learn next to move forward as a guitarist).

Most people find that the Guitar Map shows them how everything fits together and best of all, it will help you identify gaps in your knowledge that are holding you back.

(There is often just one piece of information that holds people back, 1 key insight that they need to know so they can continue moving forward and improving in their guitar journey.)

We made the Guitar Map so people like you can quickly identify what you don’t know, that you need to know next. We hope that makes sense!?

NOTE: The Guitar Map is now included in our free special report: 'The 7 Steps To Guitar Mastery'.

What Type of Guitarist Are You?

Take our 60-second quiz and see your results now: Take The Quiz

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