Three-Chord Theory2
Rockmaster Three-Chord Fact
See Why the Three-Chord Theory is Fact
Three-Chord Theory2
There are three major chords in each key. These three major chords contain all of the notes for that key and, theoretically, can be used to harmonize any melody note for that key.
We will use the key of F major to illustrate this fact, but it applies to any key.
When you harmonize the F major scale you have:
F G A Bb C D E
F Gm Am Bb C Dm Edim
I IIm IIIm IV V VIm VIIdim
The three major chords, I, IV, V are F, Bb, C.
When you form a chord you use the Root, third, and fifth of the scale to form the triad.
There are two notes left – the 6th and the 7th (b7th, 7th) . Any 4-note chord that you form will use one of these two notes. So every 4-note chord is either a 6th or a 7th chord.
To the F major triad you can add the 6th or the 7th.
I = F A C F
R 3 5 6 7
F A C D F6
F A C E Fmaj7
The notes F A C D form the F6 chord but are also Dm7, Bbmaj9, G11.
The notes F A C E form thr Fmaj7 chord but are also Dm9, G13
To the Bb major triad you can add the 6th or the 7th
IV = Bb D F Bb
R 3 5 6 7
Bb D F G Bb6
Bb D F A Bbmaj7
The notes Bb D F G form the Bb6 chord but are also Gm7, Ebmaj9, C11
The notes Bb D F A form the Bbmaj7 chord but are also Gm9, C13.
To the C major triad you can add the 6th or the b7th.
V = C E G C
R 3 5 6 b7
C E G A C6
C E G Bb C7
The notes C E G A form the C6 chord but are also Am7, Fmaj9, D11.
The notes C E G Bb form thr C7 chord but are also Am7-9, D11#5.
These are the diatonic chords in the key of F major.
Diatonic Chord Summary
F Gm Am Bb C Dm Edim
F6 = Dm7, Bbmaj9, G11
Fmaj7 = Dm9, G13
Bb6 = Gm7, Ebmaj9, C11
Bbmaj7 = Gm9, C13
C6 = Am7, Fmaj9, D11
C7 = Am7-9, D11#5
Gm = Bb6 N/5 N/5 = No 5th
Am = C6 N/5
Dm = F6 N/5
Edim = C7 N/R N/R = No Root
Play What A Wonderful World
Non-Diatonic Chords
A song can also contain non-diatonic chords. Non-diatonic chords we will define as chords that we borrow from other keys.
A very good example of this is the borrowed dominant chords. Normally, the II, III and VI chordsare minor chords, but these chords can also be dominant – II7, III7, VI7 – chords borrowed from other keys
II7 Love Walked In
III7 but I still had Georgia On My Mind.
VI7 That is so Crazy.
The Three-Chord Theory is now fact.
Other Songs That Use II7, III7, VI7 Chords
