Music Theory Reference

There are different ways to explain how chords work. We define a chord as three (or more) every other notes of scale played together. In the C major scale there are seven ways to play three every other notes, starting from C, D, E, F, G, A and B at last:

To analyze these chords, let’s measure the intervals between every other notes of the C major scale using the picture above. The interval between C and E is 2 tones, between E and G - 1.5 tones, between D and F - 1.5 tones, between F and A - 2 tones, etc.

As you can see, the difference in the intervals is a result of uneven distribution of black keys. In the cases when there are two black keys between scale notes, the interval is 2 tones. When there is only one black key - 1.5 tones:

Now let’s group our seven chords by the lengths of intervals between their notes. We get three different buckets:

1. Chords with the first interval of 2 tones and the second one of 1.5 tones. They start with the scale notes 1, 4, 5.
2. Chords with the first interval of 1.5 tones and the second one of 2 tones. They start with the scale notes 2, 3, 6.
3. Chords with both intervals of 1.5 tones. Only one chord here, starting on the scale note 7.

The chords from first bucket are called major triads or major. From the second bucket - minor triads or minor. From the third bucket - diminished triad.

Here are all the seven chords from the C major scale with their respective names:

C major triad (C)
D minor triad (Dm)
E minor triad (Em)
F major triad (F)
G major triad (G)
A minor triad (Am)
B diminished triad (Bdim)