Music Theory

Making Chords from the Major Scale

A little on chords themselves: a major chord is made up of three notes, 1st 3rd 5th (from it's major scale). A minor chord changes slightly and is made up of 1st b3rd 5th (the 3rd is dropped by a fret). You can see this in any given open chord major and minor pairing.

That being the case, we can turn the notes of the major scale into full chords by taking each degree and finding its relative 3rd and 5th. Following that process we get:

1st - Major

2nd - Minor

3rd - Minor

4th - Major

5th - Major

6th - Minor

7th - Diminished

Therefore if we took the G Major Scale, the chords in the key of G Major would be: G Am Bm C D Em F#dim.

Just like in the scale, these chords would naturally resolve to the root (G). 

Some common major keys in songs: E, G, C, A, D

Song Analysis

Here are some progressions from popular songs, the key they're in, and the chords of the key used. 

Perfect - Ed Sheeran (G)

Verse - G Em C D (I vi IV V)

Chorus - Em C G D (vi IV I V)

Blank Space - Taylor Swift (D)

Verse - D Bm G A (I vi IV V)

Chorus - D Bm Em G (I vi ii IV)

Sign of the Times - Harry Styles (F)

Verse and Chorus - F Dm C (I vi V)

Bridge - F Dm C Bb (I vi V IV)

Minor Keys

If you were to follow the same process for the C minor scale, this would be the result:

Minor Scale Degrees: 1 2 b3 4 5 b6 b7

C Minor Scale: C D Eb F G G# Bb

Minor Scale Chords: 

1 = Minor (1 b3 5)

2 = Diminished (2 4 b6)

b3 = Major (b3 5 b7)

4 = Minor (4 b6 1)

5 = Minor (5 b7 2)

b6 = Major (b6 1 b3)

b7 = Major (b7 2 4)

So the chords of the C minor scale are: Cm Ddmin Eb Fm Gm G# Bb

Relative Theory

As you may have noticed, when you look at the chord scale for the major and minor scale, the chords themselves are in the same order, just starting on a different note. That's due to relative theory. Every major key has a relative minor key, that is, a minor scale that contains all the same notes, and vice versa. Here's how:

C Major Scale Notes

 1   2   3   4   5  6   7

C  D  E  F  G  A  B

If you started that scale on the 6th degree you would get this:

6  7   1    2   3  4   5

A  B  C  D  E  F  G

Which actually is the A Minor Scale:

1   2  b3 4   5  b6 b7

A  B  C  D  E  F  G

You may also notice here that C, which was our root initially, is now the b3 of A Minor, and therein lies the relative theory basics:

The Sixth Degree of a major scale is the root of its Relative Minor

The b3 of a minor scale is the root of its Relative Major

That means both C major and A minor contain the same notes and chords, just in a different order as the root has been shifted. Here are all the relative Majors to Minor (of course, they also work the other way):

 

C Major - A Minor

C# Major - Bb Minor

D Major - B Minor

D# Major - C Minor

E Major - C# Minor

F Major - D Minor

F# Major - D# Minor

G Major - E Minor

G# Major - F Minor

A Major - F# Minor

Bb Major - G Minor

B Major - G# Minor

Seventh Chords

The basic idea of creating 7th chords comes from adding one more 3rd interval on top of your existing major or minor triad. The most common 7th chords and their formulas are as follows:

Major 7: 1 3 5 7

Minor 7: 1 b3 5 b7

Dominant 7: 1 3 5 b7

Harmonising 7th Chords

7th chords are relatively easy to fit into a diatonic key because for the most part they can be used instead of standard major and minor chords in the key. The major 7th chord scale is as follows:

1 - Maj7

2 - min7

3 - min7

4 - Maj7

5 - Dom7

6 - min7

7 - m7b5 (still to be considered dimished harmony)

Relative theory also applies to these chord scales, and so any minor key can be considered as the relative major chords beginning on the 6th degree:

1 - min7

2 - m7b5

b3 - Maj7

4 - min7

5 - min7

b6 - Maj7

b7 - Dom7