Music Theory Part 8 – Major Key 4 Note Chords

We learned in parts 1-6 about Major Scales, Minor scales, Chord formation, Keys and Relative Keys.  Revisit these earlier posts if you need to, as from now on in our Music Theory series we’ll be presuming these things to be known.

Today’s post is about the 4-note chords that can be formed from the Major and Minor Scales.  These are very often called “7th chords” as, whereas basic triads are made of root, third and fifth, 4-note chords are formed of root, third, fifth and seventh.

Again though, this “root, third, fifth and seventh” is relative.  What we mean by this is that when you’re building a chord from the D note in a C major scale (ie. from step 2 of the C major scale).  Effectively you’re using notes 2, 4, 6, and 8 from the C major scale.  However, when discussing the chord, we would still always call the notes the 1, 3, 5 and 7.  ie.  Relative the the root of the chord and not the parent scale.


4-Note Chord Formulas
I,  III,  V,  VII  =  Major7
I,  III,  V,  bVII  =  7
I,  bIII,  V,  bVII =  minor7
I,  bIII,  bV,  bVII  =  min7b5  (aka  1/2 diminished)

C Major Scale  

C  D  E  F  G  A  B

CEGB =  Cmaj7
DFAC  =  Dmin7
EGBD =  Emin7
FACE  =  Fmaj7
GBDF  =  G7
ACEG  =  Amin7
BDFA   =  Bm7b5 / 1/2dim

Above, see the 4 note chords are extracted from the Major scale in the same way as the 3 note chords, (ie. using every other note).
Again, as with all the previously studied chord formation, scales, etc, this is general and formulaic.  So we can expand this to:

Major Scale 4-note Formulas
Imaj7           IImin7          IIImin7           IVmaj7          V7          VImin7          VII m7b5

Coming Next Time – Minor Scale 4-note Formulas.

-Guitar Lessons London-