Theory lesson: chords of the major scale – diatonic chords


When you have a chord progression and want to use a scale to improvise over the top how do you know which scale to use? When you’re listening to your favourite song and trying to figure out the chords which ones do you try? If you know which chords are in each key then it will make both of these tasks easier.

Each musical key has a group of chords that go together. These chords are built from the notes of the scale attached to that key. These are known as diatonic chords.

In this lesson we will have a look at how to figure out the chords for any major key. If you haven’t already have a look a the lesson on major scales for guitar, bass, banjo or ukulele. This information will come in useful when doing this lesson.

We will use the key of C major for this lesson. it is the easiest key to use as there are no sharps or flats in the C major scale. Here are the notes of the C major scale in order.

Degree of scale
I
II
III
IV
V
VI
VII
Scale notes
 C
D
E
F
G
A
B

Each note in the scale has a chord that is associated with it. The notes for all the chords are taken from the key. Once you know the pattern to follow you can figure out what each chord is.

We already know that a C major chord is made up of the 1st, 3rd and 5th notes of the C major scale. This is the C major triad as there is only one of each note (usually when we play a chord it is bulked out with duplicates of some notes).

When we create this chord we skip the 2nd and 4th notes. If we use that pattern of skipping notes we can figure out the other chords used in the key of C major.

Degree of scale
I
II
III
IV
V
VI
VII
Type of triad
 major
minor
minor
major
major
minor
diminished
1st note of chord
C
D
E
F
G
A
B
2nd note of chord
E
F
G
A
B
C
D
3rd note of chord
G
A
B
C
D
E
F

As we can see from the table there are three types of triad found in the major scale:

  • major
  • minor
  • diminished

The major triad uses the root, major 3rd (2 tones or 4 frets) and perfect 5th (3 ½ tones or 7 frets) of the major scale. In the key of C they are C, E and G. The minor triad uses the root, minor 3rd (1 ½ tones or 3 frets) and perfect 5th which come from the minor scale. The only difference between the major and minor triads is the 3rd. A minor 3rd is one fret (or semi-tone) lower than a major 3rd. The diminished triad is a little different. This triad uses the root, minor 3rd and diminished 5th (3 tones or 6 frets). Diminished just means one fret lower (kind of like the minor 3rd). So the diminished chord is a minor chord, but sounds ‘extra minor’ due to the diminished 5th. It can take quite a while for your ears to get used to a diminished chord!

All the chords used in the key of C can be used in different keys as well. For example, the G major chord is the root chord from the key of G major and also the 4th chord from the key of D major.

Why not have a go a writing out the formulas for different keys. It’s good practice to write things down to help your brain to get around the theory!

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