Seventh Chords and Beyond

The idea

Stack another 3rd on top of a triad and you get a 7th chord, the color layer of harmony.

Chord	Formula	Sound and where it lives
maj7 (Cmaj7)	1 3 5 7	Soft, dreamy. Ballads, neo-soul, bedroom pop
7, “dominant” (C7)	1 3 5 ♭7	Bluesy, tense. The whole blues, and the V7 that pulls home
m7 (Cm7)	1 ♭3 5 ♭7	Smooth minor. Funk, R&B, mellow rock
m7♭5, “half-diminished”	1 ♭3 ♭5 ♭7	Melancholy tension. The ii chord of minor keys
dim7	1 ♭3 ♭5 ♭♭7	Maximum drama, symmetrical. A passing chord
m(maj7)	1 ♭3 5 7	Film noir, spy themes

Why the dominant 7th pulls so hard. It contains a tritone between its 3rd and its ♭7. In G7 those notes are B and F. The tritone resolves by half steps in opposite directions into the tonic chord: B goes up to C and F goes down to E. That resolution is the V7–I cadence.

Extensions (9, 11, 13) are more stacked 3rds, which is the same as scale degrees 2, 4 and 6 an octave higher. For rock and pop you mostly need:

• add9 (1 3 5 9): a triad with the 9th added and no 7th. The shimmering pop chord.
• m9 and 9: a 7th chord plus the 9th.
• The knowledge that you can leave out the 5th, and on guitar often the root too. The 3rd and the 7th carry the identity of the chord.

Sus chords replace the 3rd with a neighbor: sus2 (1 2 5) and sus4 (1 4 5). With no 3rd they are neither major nor minor: open and ringing. Dsus4 – D – Dsus2 – D is half of the acoustic-rock songbook.

On your instrument

Open chords, upgraded. Every open chord you know is one finger away from its 7th versions. Strings are listed from 6 to 1, and x means “do not play”.

Triad	maj7	Dominant 7	Minor	m7
C: x32010	Cmaj7: x32000	C7: x32310
A: x02220	Amaj7: x02120	A7: x02020	Am: x02210	Am7: x02010
D: xx0232	Dmaj7: xx0222	D7: xx0212	Dm: xx0231	Dm7: xx0211
E: 022100	Emaj7: 021100	E7: 020100	Em: 022000	Em7: 020000
G: 320003	Gmaj7: 320002	G7: 320001

Shell voicings use only the root, 3rd and 7th. They sound sophisticated, stay clean under gain, and leave room for a vocal or a lead.

Root on string 5        Root on string 6
     Cmaj7  C7   Cm7         Gmaj7  G7   Gm7
G|----4-----3----3----|  G|----4----4----3----|
D|----2-----2----1----|  D|----4----3----3----|
A|----3-----3----3----|  A|-------------------|
E|--------------------|  E|----3----3----3----|

Notice how little changes between the three types: one note moves by one fret each time.

Piano. Comp with the root in the left hand and the 3rd and 7th (the “guide tones”) in the right. For ii–V–I in C: Dm7 is D with F and C. G7 is G with F and B. Cmaj7 is C with E and B. Only one right-hand note moves at each change.

Worked example

The same loop, plain and upgraded:

Version	Chords	Effect
Plain	Am – F – C – G	Solid, anonymous
Upgraded	Am7 – Fmaj7 – Cadd9 – Gsus4 → G	Softer, wider, more personal

On guitar the upgraded version is easier, not harder: Am7 is x02010, Fmaj7 is xx3210, Cadd9 is x32030, Gsus4 is 320013 resolving to 320003. Several notes ring through all four chords, and that is exactly why it sounds connected.

Exercises

1. Take Am – F – C – G and play the upgraded version from the worked example. Record both and describe the emotional difference in one sentence.
2. Find the tritone inside the open G7 shape: B on string 5 and F on string 1. Move each one a half step to its resolution in a C chord. Then find the tritone of E7 (G♯ and D) and resolve it into Am.
3. Write a four-chord progression where every chord is a sus2, sus4 or add9. This is the shimmering indie and post-rock sound: The Edge, plus delay.
4. Play a 12-bar blues in A with shell voicings only: A7, D7 and E7.

Common mistakes

• Confusing maj7 and 7. Cmaj7 has B. C7 has B♭. One is a dream and the other is a question.
• Confusing add9 and 9. Cadd9 has no 7th. C9 is a dominant chord with a ♭7 in it, and it has a completely different job.
• Using 7th chords everywhere. Under heavy distortion most of them turn to noise. Module 3.3 covers what works there.

Check yourself