The octave: the same note, another floor
A octave is the distance of 12 half steps between two notes with the same name. A 440 Hz and A 880 Hz are an octave apart: the frequency doubles. That's why they blend so well they seem like “the same note”.
Octave inside the chord (doubling)
Add the root an octave up doesn't change the chord type: C–E–G–C is still C. Repeating a chord note in another octave is called doubling. That's why chord symbols never write “8”: the octave doesn't create a new chord, it just makes the sound fuller.
On the guitar doubling is the rule: the open G chord (G B D G B G) has three Gs, two Bs and one D.
Power chord (C5): root, fifth and octave
O power chord, or fifth chord, is the most famous chord “with an octave”. It has only the root, the fifth and the octave. Since has no third, it's neither major nor minor. In chord symbols it shows up with the number 5: C5, E5, A5.
On acoustic and electric guitar, the shape is always the same and can slide along the neck: finger 1 on the root (6th or 5th string), finger 3 two frets higher on the next string down (fifth) and finger 4 on the same fret of the following string (octave). It's the foundation of rock and punk.
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Open the free app →Beyond the octave: 9th, 11th and 13th
Keep stacking thirds after the seventh and you go past the octave. The new notes are the same as in the scale, but counted in the octave above:
| Range | It's the same note as… | Half steps | In C |
|---|---|---|---|
| 9ª | 2nd + octave | 14 | D |
| 11ª | 4th + octave | 17 | F |
| 13ª | 6th + octave | 21 | A |
We call them 9, 11 and 13 (not 2, 4 and 6) when the note is a addition on top of the full chord, usually with the seventh. Extensions can be altered: ♭9, ♯9, ♯11, ♭13.
Ninth chords
| Chord symbol | Notes in C | What it has |
|---|---|---|
| C(9) or Cadd9 | C E G D | Major triad + ninth, without the seventh |
| C7(9) | C E G B♭ D | Dominant seventh + ninth |
| C7M(9) | C E G B D | Major seventh + ninth |
| Cm7(9) | C E♭ G B♭ D | Minor seventh + ninth |
| Cm(9) or Cm(add9) | C E♭ G D | Minor triad + ninth |
No seventh: just extra brightness.
Very common in samba and jazz.
Typical bossa nova sound.
Suspended chords: sus2 and sus4
In chords sus the third leaves and is replaced by the 2nd or the 4th. Without a third, the sound is “suspended”, neither major nor minor, and it usually goes back to the normal chord.
On the guitar, Dsus4 → D → Dsus2 → D is a classic embellishment: only the fingers on the 1st string change.
Notice: on the sus2 the note D replaces the third (and is called 2). In the add9 the third stays and the D is an addition (and is called 9).
Sixth chord
C6 = C E G A: major triad with the major 6th. It sounds sweet and “round”, very common in samba, bossa and swing. Cm6 = C E♭ G A.
11ª e 13ª
- 11ª: the 4th an octave up. It's more common in minor chords, like Am7(11) = A C E G B. In major chords it usually appears augmented: C7M(♯11).
- 13ª: the 6th an octave up. Widely used on the dominant: G7(13) = G B D F E.
Lots of notes, few hands: what you can leave out
A 13th chord would have seven notes! In practice, musicians leave out the less important notes:
- The perfect 5th is the first to go: it barely changes the sound.
- The root can be dropped if the bass player is already playing.
- The 3rd and 7th never get left out: they define the chord type.
Now put the theory into your fingers
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Practice theory in the free appFrequently asked questions
Why doesn't the octave show up in chord symbols?
Because repeating the root an octave higher doesn't change the chord type. C with a doubled C is still C.
What is a fifth chord or power chord?
A chord with just the root, the fifth and usually the octave. It has no third, so it's neither major nor minor. Chord symbol: C5, E5, A5.
What's the difference between C9 and C(9)?
In Brazil many people write C9 meaning C(9): C with an added ninth and no seventh. In American notation, C9 includes the minor seventh. If you see C7(9), there's no doubt: it has both the seventh and the ninth.
What's the difference between sus2 and add9?
In sus2 the 2nd replaces the third (C D G). In add9 the third stays and the ninth is added (C E G D).