Seventh chords: add a fourth note
Build the three most common seventh chords, hear why the dominant seventh pulls so hard towards home, and tell it from the softer major seventh and minor seventh.
FOUR NOTES
A triad plus a seventh
A seventh chord is a triad with one more third stacked on top. The new note is a seventh above the root. Two sizes matter: the minor seventh, 10 half steps above the root, and the major seventh, 11 half steps, just one half step below the root's octave (12).
From C: C to B♭ is 10 (minor seventh), C to B is 11 (major seventh), C to the next C is 12. Which triad you start with and which seventh you add gives the chord its name.
G7, the dominant seventh, counted in half steps from G.
G to B 4 major third
G to D 7 perfect fifth
G to F 10 minor seventh
Inside it: B to F = 6, a tritoneG7 = G B D F = major triad + minor seventh (0, 4, 7, 10)The B–F tritone is the restless gap from the diminished chord B–D–F. In fact the top three notes of G7 are exactly B–D–F.
Check yourself
Behnam has a G major triad, G–B–D, and wants to turn it into G7. Which note should he add on top?
- F♯, 11 half steps above G
- E, 9 half steps above G
- F, 10 half steps above G
- A, 2 half steps above G
Show the answer
F, 10 half steps above G
Right. A dominant seventh is a major triad plus a minor seventh, and 10 half steps above G is F. G–B–D–F.
| Chord | Triad | Seventh on top | Example | What most people hear |
|---|---|---|---|---|
| Dominant 7th (G7) | major | minor 7th (10) | G B D F | leaning, wants to move |
| Major 7th (Cmaj7) | major | major 7th (11) | C E G B | soft, shimmering, jazzy |
| Minor 7th (Am7) | minor | minor 7th (10) | A C E G | mellow, relaxed |
WHY G7 PULLS
Two notes that want to move by a half step
Inside G7, B sits one half step below C and F sits one half step above E. Most ears hear both as unfinished: B wants to rise to C, F wants to fall to E. When the next chord is C–E–G, both land at once. That is why G7 to C is one of the strongest 'arriving home' moves in music.
On the keyboard: B→C is the next key up, F→E is the next key down. Two tiny steps, and the tension of the B–F tritone resolves.
Check yourself
Sam ends his song on G7 instead of C. Most listeners will hear the song as finished.
Show the answer
False
False. G7 is the chord that most strongly wants to move on: its B wants to rise to C and its F wants to fall to E. Ending there usually sounds like a question left open. Ending on C lets both notes land.
The two calm sevenths
Major 7th · C E G B
The top note B is only one half step below the C an octave above the root. Most listeners hear that close rub as a soft shimmer, the sound of many jazz and soul ballads. It can sit still without needing to move.
Minor 7th · A C E G
A minor triad with G on top, two half steps below the octave A. The rub is gentler, and most people hear the chord as mellow and relaxed. It also rests comfortably.
Naming a seventh chord by ear
- Does it want to move?
If the chord leans hard towards the next one, as if it can't stop there, your first guess is a dominant seventh.
- If it can rest, listen to the top note
A close, shimmering rub just under the root's octave points to a major seventh. A softer, rounder top points to a minor seventh.
- Check the triad underneath
Hum the root and the middle note, as in the major and minor lesson. A major triad under a calm seventh means major 7th; a minor triad means minor 7th.
Check yourself
Count from the root: which kind of seventh chord?
- G B D F
- C E G B
- A C E G
- D F♯ A C
- F A C E
- D F A C
Show the answer
Dominant 7th (4, 7, 10): G B D F, D F♯ A C
Major 7th (4, 7, 11): C E G B, F A C E
Minor 7th (3, 7, 10): A C E G, D F A C
Check yourself
Match what you hear to the most likely chord
Show the answer
- Leans hard, and C–E–G sounds like home after it → G7
- Calm, with a shimmering rub a half step under the octave → Cmaj7
- A relaxed minor chord with a soft extra note on top → Am7
- Settled, full, but only three note names → C major triad
Check yourself
Arash is working out a song in the key of C. One chord makes him lean forward, and the chord right after it, C, feels like arriving home. Which chord is the first one most likely to be?
- Cmaj7, because it has a seventh
- G7
- Am7, because it is a seventh chord in C
- Fmaj7, because it has F in it like G7
Show the answer
G7
Yes. The leaning sound and the landing on C are the signature of G7: B rises to C and F falls to E.
Lesson recap
- A seventh chord is a triad plus a note a seventh above the root: minor seventh = 10 half steps, major seventh = 11.
- Dominant 7th = major triad + minor 7th (G–B–D–F). Its B and F pull to C and E, so it leans hard towards C.
- Major 7th = major triad + major 7th (C–E–G–B): a soft, shimmering rub that can rest.
- Minor 7th = minor triad + minor 7th (A–C–E–G): most people hear it as mellow.
- By ear: does it want to move? If not, listen to the top note's rub and the triad underneath.