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The first thing we need to know is that Chords are built from scales. A Chord is a combination of three notes or more. The combination of three notes is called "Triad". Chords are built off of a single note called the "Root". The "Triad" is a class of chords, specifically three-note chords formed by this formula: 1-3-5 or "Root", "Third", "Fifth". The order of chords in a song or section of song is called "Progression".

Diatonic triads are triads or chords that belong to a key. The definition of a triad is 3 notes and the definition of a chord is 3 or more notes so you can call these either at this point. Once we add more notes to our triad we will want to call them chords. Below the example in key of C :

We end up with a series of major and minor chords with the seventh one called diminished. These are the chords belonging to the key of C. Because all major scales are built the same way :

  • the I, IV and V chords will always be major
  • the ii, iii, vi will be minor
  • and the vii will be diminished

Note we will use upper case roman numerals to indicate major and lower case for minor.

While it's great to have a decent repertoire of memorized chords, understanding how chords are formed and named extends your chord knowledge considerably. A knowledge of chord construction gives you the ability to play chords that you've never previously learned just by seeing the chord's name and understanding what the name actually means. It also allows you to modify chords based on "sound" musical knowledge rather than guesswork. For those who want to improvise over chord progressions, it's an advantage to know which notes belong to the chord being played and which don't, so that they can target those essential chord tones accurately, and treat non-chord tones accordingly.

Name of a chord reveals it's structure. In other words the notes we have to play together. See the example below :

chord example

Like I said the name of a chord reveals its structure. Vice versa the knowledge of a structure makes the name of the chord. Here some resources for the identification of the structure or find out the name of the chords.

Another very useful resource about Chords construction, names and scales.

Here is an overview over some often used chords in the most common played keys. Below the list of most important used chords and their structures (chord degrees).



C (or Ctriad) 1 3 5 C E G
C6 1 3 5 6 C E G A
C6/9 1 3 5 6 9 C E G A D
Cmaj7 1 3 5 7 C E G B
Cmaj9 1 3 5 7 9 C E G B D
Cmaj7#11 1 3 5 7 #11 C E G B F#
Cmaj7#5 1 3 #5 7 C E G# B
C- (or Cmin or Cm) 1 b3 5 C Eb G
C-6 1 b3 5 6 C Eb G A
C-6/9 1 b3 5 6 C Eb G A D
C-7 1 b3 5 b7 C Eb G Bb
C-7#5 1 b3 #5 b7 C Eb G# Bb
C-9 1 b3 5 b7 9 C Eb G Bb D
C-11 1 b3 5 b7 (9) 11 C Eb G Bb (D) F
C-∆7 1 b3 5 7 C Eb G B
C-∆9 1 b3 5 7 9 C Eb G B D
C7 1 3 5 b7 C E G Bb
C7b5 1 3 b5 b7 C E Gb Bb
C7#5 1 3 #5 b7 C E G# Bb
C7b9 1 3 5 b7 b9 C E G Bb Db
C7#9 1 3 5 b7 C E G Bb D#
C7#11 1 3 5 b7 C E G Bb F#
C9 1 3 5 b7 9 C E G Bb D
C11 1 (3) 5 b7 9 11 C (E) G Bb D F
C13 1 3 5 b7 C E G Bb D (F) A
C7b5b9 1 3 b5 b7 b9 C E Gb Bb Db
C7#5#9 1 3 #5 b7 #9 C E G# Bb D#
C7b5#9 1 3 b5 b7 #9 C E G# Bb D#
C7#5b9 1 3 #5 b7 b9 C E G# Bb Db
C7alt any C7 with both fifth and ninth altered
C7/4 1 (3) 5 b7 11 C (E) G Bb F
C7sus4 1 4 5 b7 C F G Bb
C7susb9 1 4 5 b7 b9 1 4 5 b7 b9
C-7b5 (or Cmin7b5 or CØ) 1 b3 b5 b7 C Eb Gb Bb
C-7b5/#2 (or Cmin7b5/#2 or CØ #2) 1 b3 b5 b7 9 Eb Gb Bb D
C-11b5 (or Cmin11b5) 1 b3 b5 b7 (9) 11 C Eb Gb Bb (D) F
Cdim (or C°) 1 b3 b5 C Eb Gb
Cdim7 (or C°7 or simply C°) 1 b3 b5 bb7 C Eb Gb Bbb