Major Scale In Triads
In the first part of this lesson, we will build triad chords. Those chords are made of three notes stacked in thirds. Let's take the C major as the first approach, it is the one that everyone knows and there are no # or b in it.
We will create a first chord starting from the first note of the C major scale (C). We just need to stack the third of C (E) and the third of E (G) with the root note (C). Here is our first triad, the C major chord (C-E-G).
This chord includes a major third interval (C-E) and a minor third interval (E-G). In other words, this chord is formed starting on C, jumping D and taking E, jumping F and taking G of the C major scale.

C major chord
| C major scale |
C |
D |
E |
F |
G |
A |
B |
| C major chord (triad) |
C |
X |
E |
X |
G |
X |
X |
The second chord that we will build is a minor triad. It is made up by stacking thirds too. A minor third (F) and a major third (A) are stacked with the root note (D). As it starts from the note D, it is a D minor chord (D-F-A).

D minor chord
| C major scale |
C |
D |
E |
F |
G |
A |
B |
| D minor chord (triad) |
X |
D |
X |
F |
X |
A |
X |
If we do the same with the 5 other notes of the scale, we get 5 other chords. We obtain major and minor chords, with one exception: the degree VII stack 2 consecutive minor thirds, that gives a diminished triad.
Here are the seven chords obtained after the harmonization. There are 3 major chords (I-IV-V), three minor chords (II-III-VI) and one diminished (VII).
Whatever the major scale used, the principle is the same. The first chord is major, the second is minor and so on.
| Degrees |
I |
II |
III |
IV |
V |
VI |
VII |
| C major scale |
C |
D |
E |
F |
G |
A |
B |
| Triad chords |
C |
Dm |
Em |
F |
G |
Am |
Bdim |
Harmonisation of the major scale in triads