Chord Types Explained: Sus, Add9, 7ths, Diminished, Augmented and More

Sooner or later every songwriter runs into chord names like Cadd9, Csus4, A7, Cmaj7, Bdim and Caug and wonders what they mean. The good news is that these names follow a simple system. Once you can read them, you can make a plain progression sound richer, add tension where you want the song to push forward, and connect chords more smoothly. This guide explains what each chord type is, how it relates to the basic major or minor chord it comes from, and when to use it in a song.

How to Read a Chord Name

A chord name has two parts: a letter, and sometimes something after it.

The letter is the root. The root is the note the chord is built on and named after. In every C chord below, C is the root.
Nothing after the letter means a major triad. A triad is a three-note chord: the root, the 3rd and the 5th. "C" by itself means C major.
"m" means the 3rd is minor (lowered). "Cm" is C minor.
A number names a note added or stacked on top. You count it up the major scale of the root. The C major scale is C D E F G A B, so in C, the 2nd is D, the 4th is F, the 6th is A, and the 9th is D again, an octave higher.
"maj7" means a major 7th is added. A plain "7" always means a minor 7th. That chord is called a dominant 7th.
"sus" means the 3rd is replaced by another note.
"add" means a note is added without the 7th.
"dim" lowers the 3rd and the 5th. "aug" (sometimes written +) raises the 5th.

Two distances will come up again and again. A half step is the distance of one fret. A whole step is two frets.

The 3rd Decides Major or Minor

Start with the two basic chords that everything else is compared to.

C major: 1 3 5, notes C E G. The plain, stable major chord.
C minor (Cm): 1 b3 5, notes C Eb G. The plain minor chord.

The only difference is the middle note: E in C major, Eb in C minor. That note is the 3rd, and it is what makes a chord sound major (bright) or minor (dark). Play C and Cm back to back and listen to that one note change.

Here is the most useful idea in this whole article: most variations keep the main chord's job in the progression and only change its color. Cadd9, Csus2, C6 and Cmaj7 can all stand in for C. Dm7 can stand in for Dm. G7, G9, G7sus4 and G13 all do G's job as the chord that leads home to C. The variation changes the sound, not the direction of the progression.

Chords With No 3rd

Since the 3rd decides major or minor, a chord without a 3rd is neither. These chords sound open and neutral.

Power chord: C5

Formula 1 5, notes C G. Just the root and 5th. It stays clear under heavy distortion, which is why rock and metal players use it in place of major or minor chords.

Sus4: Csus4

Formula 1 4 5, notes C F G. The 3rd (E) is replaced by the 4th (F). The F wants to fall a half step to E, so Csus4 usually resolves to C. "Resolve" just means moving from a tense chord to a stable one. Listen for the small drop when you go from Csus4 to C.

Sus4 is very common on the V chord before going home. In the key of C, the V chord is G, the chord built on the 5th note of the scale. So you will often hear Gsus4 - G - C.

Sus2: Csus2

Formula 1 2 5, notes C D G. The 3rd is replaced by the 2nd. It pulls less than sus4, so it can resolve to C or simply be used in place of C. It is common on the I and IV chords (built on the 1st and 4th notes of the scale, C and F in the key of C) in pop, rock and worship music, especially with open strings.

Added-Note Chords

These keep the full major chord and add one extra note on top. They are stable and do not need to resolve.

Add9: Cadd9

Formula 1 3 5 9, notes C E G D. A C major chord with the 9th (D) added and no 7th. It sounds brighter and more ringing than plain C. Use it anywhere a plain major chord fits, most often on I and IV in pop and acoustic music.

Sixth: C6

Formula 1 3 5 6, notes C E G A. A major chord with the 6th added. It sounds warm and settled, and it is a classic final chord in swing, jazz and old pop. C6 uses the same notes as Am7, so which one you hear depends on the bass note and the chords around it.

Seventh Chords

Seventh chords add a fourth note: the 7th. Which 7th you add makes a big difference.

Major 7th: Cmaj7

Formula 1 3 5 7, notes C E G B. The B sits a half step below the root. It sounds soft and relaxed. Cmaj7 stands in for I or IV in jazz, soul, R&B and ballads. It is a resting chord and does not need to resolve.

Minor 7th: Cm7

Formula 1 b3 5 b7, notes C Eb G Bb. A minor chord with the minor 7th. Smoother and mellower than plain minor. It can stand in for any minor chord. Dm7 is the ii chord (built on the 2nd note, D) in the jazz ii-V-I.

Dominant 7th: C7, G7 and A7

C7 has the formula 1 3 5 b7, notes C E G Bb. It is a major chord with the minor 7th, and it is tense. It wants to move to the chord a 5th below: C7 goes to F.

The most important dominant 7th in the key of C is G7: notes G B D F. Watch two notes when it moves to C:

The 3rd, B, rises a half step to C.
The 7th, F, falls a half step to E.

Those two notes pulling inward are why G7 to C sounds so final.

A7 has the notes A C# E G. In the key of C major, C# is not in the key. A7 acts as a secondary dominant: a dominant 7th that points at a chord other than home. A7 leads to Dm, the chord a 5th below A, just as G7 leads to C.

One exception: in the blues, 7 chords on I, IV and V are used as stable, bluesy sounds instead of tense ones.

Ninth: C9

Formula 1 3 5 b7 9, notes C E G Bb D. A dominant 7th with the 9th on top. It does the same job as C7 with a fuller sound, common in funk, blues and soul.

7sus4: C7sus4

Formula 1 4 5 b7, notes C F G Bb. A dominant 7th with the 4th in place of the 3rd. It holds the tension of a 7 chord without committing. It often resolves to C7, then on to F.

Tense Passing Chords

These chords are unstable. You usually play them briefly, on the way to somewhere else.

Diminished: Bdim

Formula 1 b3 b5, notes B D F. This is the vii chord in C major (built on the 7th note, B). It has the same notes as G7 without the G, so it does the same job: it leads to C.

Half-diminished: Bm7b5 and Dm7b5

Bm7b5 has the formula 1 b3 b5 b7, notes B D F A. It is the 7th chord on vii in C major. In a minor key, this type of chord is the ii chord. In C minor that is Dm7b5, notes D F Ab C, and Dm7b5 - G7 - Cm is the minor ii-V-i.

Diminished 7th: C#dim7

Formula 1 b3 b5 bb7, notes C# E G Bb. It is built from minor 3rds stacked all the way up, so it is symmetrical. The double-flat 7th sounds the same as a major 6th. It resolves up a half step: C#dim7 leads to D or Dm. Use it between two chords a whole step apart, like C and Dm7.

Augmented: Caug and Gaug

Caug has the formula 1 3 #5, notes C E G#. It is a major chord with the 5th raised, and it sounds unstable and floating. The G# wants to keep rising to A, so it leads well to F or Am, which both contain A.

Gaug, notes G B D#, is an augmented V chord. Its D# rises a half step to E, so Gaug leads strongly to C.

Using Them in Progressions

Play through these in the key of C (unless noted) and listen for the moves described.

C - Csus4 - C: the F in Csus4 falls back to E.
C - F - Gsus4 - G - C: the sus4 delays the V chord before going home.
Cadd9 - G - Am7 - Fmaj7: the common I-V-vi-IV pop progression with color added. Same progression, same direction.
Dm7 - G7 - Cmaj7: the jazz ii-V-I.
C - A7 - Dm - G7 - C: A7 points at Dm, then G7 points home.
C - C#dim7 - Dm7 - G7: the dim7 fills the whole step between C and Dm7.
C - Caug - F: G rises to G#, then to A.
C - Caug - C6 - C7 - F: one note climbs G, G#, A, Bb while the rest stay.
Am - Am(maj7) - Am7 - Am6: one note falls A, G#, G, F#. This is a classic minor "line cliche."
Dm7b5 - G7 - Cm: the minor ii-V-i, key of C minor.
C7 - F7 - C7 - G7: blues, with dominant 7ths used as stable chords.

When to Reach for What

Richer sound, same direction: add9, sus2, maj7, m7, 6.
Tension that pushes to the next chord: 7, 9, sus4, 7sus4, aug, dim, dim7.
Delay an arrival: a sus4 before its major chord.
Connect two chords smoothly: a passing dim7 or aug chord, or a line that moves one note at a time.
A darker, borrowed feel or jazz minor keys: m7b5.

For practice, take a simple progression you already know, such as C - F - G - C. Play it plain, then change one chord at a time: try Cadd9 for C, Fmaj7 for F, and Gsus4 - G or G7 before the last C. Play each version a few times and decide which sound you like. Do this with a few progressions every week and these chords will start to feel like normal choices instead of strange names.

Try these in the chord progression builder: click any chord name in your progression to change it to a sus, add9, 7th or other type, then step through the ways to play it.