Chord Theory

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The notes that make up a chord can be related to the major scale of that chord’s root note eg. for a D chord – the D major scale. The basic major ‘triad’ chords (eg. A, Bb, B, C etc.) are made up of the 1st, 3rd and 5th notes from their respective major scales. In other types of chords notes are either adjusted slightly, as in minor (m) chords where the ‘3rd’ is flattened by a half-step (commonly referred to as a b3,) or extra notes are added as in major 7 (maj7) chords where the 7th note of the major scale is added to the basic triad. Sometimes both these things happen at the same time, for instance in a 7 chord the 7th is added to the chord but flattened at the same time, so it is called a b7 within the chord.

In the first table below you can see chord formulas relating to the major scale for various types of chords. The examples use C as the root note but you can use the second table, showing all the major scales, to work out the notes used in chords of other keys.

This is a relatively basic way of thinking about how chords are constructed. It doesn’t explain everything but hopefully it will help you on your way to a better understanding of how scales and chords relate to each other.

Type of Chord Chord Symbol in C Notes in Chord Chord Formula
Major C C E G 1 3 5
Minor Cm C Eb G 1 b3 5
7th C7 C E G Bb 1 3 5 b7
Minor 7th Cm7 C Eb G Bb 1 b3 5 b7
Major 7th Cmaj7 C E G B 1 3 5 7
Minor 7th Flat 5th Cm7b5 (or Cø) C Eb Gb Bb 1 b3 b5 b7
Suspended 4th Csus4 C F G 1 4 5
Diminished Cdim (or Co) C Eb Gb 1 b3 b5
Augmented Caug (or C+) C E G# 1 3 #5
6th C6 C E G A 1 3 5 6
Minor 6th Cm6 C Eb G A 1 b3 5 6
6th Add 9th C6add9 C E G A D 1 3 5 6 9
9th C9 C E G Bb D 1 3 5 b7 9
Minor 9th Cm9 C Eb G Bb D 1 b3 5 b7 9
Major 9th Cmaj9 C E G B D 1 3 5 7 9
Scale note numbers 1 2 3 4 5 6 7
A major scale A B C# D E F# G#
Bb major scale Bb C D Eb F G A
B major scale B C# D# E F# G# A#
C major scale C D E F G A B
Db major scale Db Eb F Gb Ab Bb C
D major scale D E F# G A B C#
Eb major scale Eb F G Ab Bb C D
E major scale E F# G# A B C# D#
F major scale F G A Bb C D E
Gb major scale Gb Ab Bb Cb Db Eb F
G major scale G A B C D E F#
Ab major scale Ab Bb C Db Eb F G