Harmonising scales
To harmonise a scale is to build chords on each note of the scale, using only the notes found in this scale.
Usually a piece or section of music is derived from one scale. This means that all melodies and chords will only use the notes found in the chosen scale.
Frequently the scale that is chosen is a major one. However, any scale could be used.
To write a melody you would use the notes of a scale individually.
To build chords from the notes of your chosen scale you should harmonise the scale at third intervals using only the notes found in your chosen scale.
HARMONISING THE MAJOR SCALE
Chords are built using third intervals.
So, to build a chord on the first note of the C major scale ‘C’, you would add the note that is a third higher than ‘C’. This is ‘E’.
C : D : E
1 : 2 : 3
Next, add the note which is a third higher than ‘E’.
This is ‘G’ and results in a chord built on the first note of the scale containing the notes C:E:G.
When you continue this process on each note of the C major scale you get the following combinations of notes.
G A B C D E F G
E F G A B C D E
C D E F G A B C
These combinations of notes have the following chord names:
C Dm Em F G Am Bo C
m = minor chord
o = diminished chord (1:b3:b5)
This results in the formula: M m m M M m 0 M
M = Major chord
m = minor chord
o = diminished chord
This formula can be applied to any major scale. It will tell you the type of chord that is built on each of its notes. For example the chord built on the third note of any major scale will always be a minor (m).
When you add another note, once again a third up from the previous one, you get a series of chords each built of four notes. Below is the formula to name these chords in the major scale:
Maj7 m7 m7 Maj7 7 m7 
Maj7
= m7b5
The table below shows all the three and four note chords in all major scales.
HARMONISING the ‘A Harmonic Minor’ scale
If your chosen scale was ‘A’ Harmonic Minor the notes of the scale would be:
A B C D E F G# A
Chords are built using third intervals. So, to build a chord on the first note of the scale ‘A’, you would add the note which is a third higher. This is ‘C’.
Next you would add the note which is a third higher than ‘C’. This is ‘E’ and results in a chord built on the first note of the scale containing the notes A:C:E.
When you continue this process on each note of the scale you get the following combinations of notes.
These combinations of notes have the following chord names:
+ = augmented chord (1:3:#5)
This results in the following formula:
m o + m M M o m
+ = augmented chord (1:3:#5)
M = major chord (1:3:5)
m = minor chord(1:b3:5)
o = diminished chord (1:b3:b5)
This formula can be applied to any harmonic minor scale. It will tell you the type of chord that is built on each of its notes.
For example the chord built on the third note of any harmonic minor scale will always be an augmented (+).
NOTE – All scales can be harmonised by using the same method.
© Carlos Thrale 2014 / 2020