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Harmonising the Major Scale

Adi Hughes

Adi Hughes

The first step to harmonising the major scale is understanding the fundamentals of chords and keys.

Every key contains a series of chords, one for each individual note of the scale. For this lesson, we shall use the key of G major to understand which chords and why.

What Notes Make Up the G Major Scale?

Firstly, we need to know the notes of G major. The easiest ways of doing this are:

  1. Playing the major scale starting on a G note, and writing down the notes that fall under your fingers.
  2. Counting up the steps from the root note (G) using the following formula:

Tone Tone Semitone Tone Tone Tone Semitone

The result is shown in the table below:

Chord Interval Numbers in the Key of G Major

Each chord is numbered according to its interval number, relative to the key (G). This is where chord progressions come from; a I – V – IV progression would be G – D – C. However, we don’t yet know if they are major or minor chords.

What Chords Make Up the G Major Scale?

To discover this, we identify the chord tones relative to each note, and measure against the following formula:

Major, Minor, and Diminished Chord Structures

Let’s start with the I chord.

Finding the I Chord

In G major, the 1st, 3rd and 5th notes are G, B and D. If we look at the interval quality of those notes, we get the following intervals: I – III – V. This means that, using the chord formula, the I chord in the key of G is a G major chord.

Finding the II Chord

Let’s move on to the II (A) chord.

If we now treat the A note as note 1, then the 3rd and 5th notes are C and E respectively. Here is the key of A major:

Chord Interval Numbers in the Key of A Major

The notes in our chord are A, C and E.

The 1st and 5th intervals match. However, the 3rd interval, C, has been flattened (from C#). If the 3rd note in any chord or scale is flattened, it gives it a minor tonality.

Our II chord is:

II Chord in the Key of G

We figured this out by using the notes from the G major scale to construct our chord, and then comparing our chord to its own major key to measure the interval value.

You can also do this by measuring the intervals in steps. E.g., a major third is two tones above the root. You could also use shapes or your ears to identify the intervals.

Finding the IV Chord

Let’s do the IV (D) chord.

Below is D major:

Chord Interval Numbers in the Key of D Major

None of our notes (D, F# and A) have been altered, meaning our V chord is: I – III – V = D major.

The Results

If we continue this process of building a chord from each note of the scale, we end up with the following chord sequence:

Chords in the Key of G Major

This pattern will apply to all major keys, so once you’ve completed the exercise, you needn’t do it again for every key you wish to play. However, completing the exercise is a good introduction to understanding major and minor harmony.

About the Author

Adi Hughes is an experienced guitar tutor based in Andover, Hampshire. Find out more at

Our goal is to provide you with the training, inspiration, motivation and confidence to become the guitarist you dream of becoming.

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