A chord is the combination of two or more, but usually three or more notes played simultaneously.
Chords are the basic foundation of musical harmony.
Figure 1: A C major chord.
To build any chord, a basic understanding of intervals is necessary.
When a note within a chord is altered by an accidental, a new chord quality is imposed:
Figure 2: A major triad becomes minor by flattening the third.
A dyad is a chord of two notes.
Although they are quite rare, a dyad containing a root and fifth is still used today:
|Fifth Chord||R, 5|
A triad is a chord of three notes, usually containing a root, third, and fifth.
The following is a list of triad chord formulas:
|Major||R, 3, 5|
|Minor||R, b3, 5|
|Aug||R, 3, #5|
|Dim||R, b3, b5|
|Sus4||R, 4, 5|
|Sus2||R, 2, 5|
A sixth chord is a chord of four notes, containing a root, third, fifth, and sixth.
There are only two sixth chords:
|6||R, 3, 5, 6|
|m6||R, b3, 5, 6|
A seventh chord is a chord of four or more notes, usually containing a root, third, fifth, and seventh.
The following is a list of seventh chord formulas:
|Maj7||R, 3, 5, 7|
|7 (Dominant)||R, 3, 5, b7|
|m7||R, b3, 5, b7|
|m7b5||R, b3, b5, b7|
|Dim7||R, b3, b5, bb7|
|m(Maj7)||R, b3, 5, 7|
|7(sus4)||R, 4, 5, b7|
|m7(sus4)||R, b3, 4, 5, b7|
|7(#5)||R, 3, #5, b7|
|7(b5)||R, 3, b5, b7|
A ninth chord is a chord of five notes, containing a root, third, fifth, seventh, and ninth.
The following is a list of ninth chord formulas:
|Maj9||R, 3, 5, 7, 9|
|9||R, 3, 5, b7, 9|
|m9||R, b3, 5, b7, 9|
|6/9||R, 3, 5, 6, 9|
|7(#9)||R, 3, 5, b7, #9|
|7(b9)||R, 3, b5, b7, b9|
Here are some other chords that contain intervals great than a ninth, or anything else not listed:
|add9||R, 3, 5, 9|
|11||R, 3, 5, b7, 9, 11|
|13||R, 3, 5, b7, 9, 11, 13|
|Maj7(#11)||R, 3, 5, 7, #11|
|Maj9(#11)||R, 3, 5, 7, 9, #11|
|6/9(#11)||R, 3, 5, 6, 9, #11|
A chord inversion (also slash chord) is the rearranging of notes within a given chord.
Notes can only be strictly moved up or down an octave to impose a new chord inversion.
Root position has the tonic note in the bass of a chord:
Figure 3: Three different chords in root position.
1st inversion has the note above the tonic in the bass of a chord:
Figure 4: Three different chords in 1st inversion.
2nd inversion has the second note above the tonic in the bass of a chord:
Figure 5: Two different chords in 2nd inversion.
3rd inversion has the third note above the tonic in the bass of a chord:
Figure 6: A seventh chord in 3rd inversion.
It is possible to do greater than 3rd inversion for chords that contain more than four notes (i.e. 9th, 11th, and 13th chords).
Also see Chord Progressions | Cadences.