Chord extensions: 6ths, 9ths, 11ths and 13ths

Seventh chords stack three thirds. Keep stacking and you reach the 9th, 11th and 13th: the extensions. They add colour without changing what the chord does, which is why they are everywhere in soul, funk, jazz and R&B. On guitar you cannot play every note, so the skill is knowing which notes matter and which to leave out.

By the end of this lesson you will be able to:

• Explain where the 9th, 11th and 13th come from, and what a 6 chord is.
• Play C6, Cmaj9, C9, E9, Em9, A7sus4 and G13.
• Substitute extended chords into a ii-V-I progression.

A triad stacks two thirds: 1, 3, 5. A seventh chord adds a third more: 1, 3, 5, 7. Keep stacking and you get the extensions:

• 9th: the 2nd, an octave up.
• 11th: the 4th, an octave up.
• 13th: the 6th, an octave up.

The chord's type (major 7, dominant 7, minor 7) still decides what the chord does. Extensions add colour: C9 still behaves like C7, only richer.

A 6 chord is different: it adds the 6th to a plain triad, with no 7th. C6 is C E G A. It sounds sweet and a little vintage.

Choosing what to leave out. A 13th chord has seven notes; the guitar has six strings, and fingers to spare for maybe four. Guitarists keep the notes that define the chord:

• the 3rd (major or minor)
• the 7th (which kind)
• the extension you want to hear

and leave out the 5th (it adds little) and often the root (the bass player usually has it). The G13 shape in this lesson has only four notes: root, ♭7, 3 and 13.

About the 11th. A natural 11th clashes with a major 3rd. On dominant chords, guitarists use 7sus4 instead: no third, and the 4 is the 11. On minor chords, the 11 is fine.

Hearing an extension.

1. Play C7 (x-3-2-3-1-0). Then play C9 (x-3-2-3-3-3). The only real change is on the top: the B string moves to D (the 9) and the high e moves to G.
2. Play G7, then G13 (3-x-3-4-5-x). The E on the B string is the 13th. Notice there is no D (the 5th) and no A (the 9th) in this voicing.
3. Play E7, then E9: the high e moves to fret 2 (F♯).

The ii-V-I. Play Am7, D9 (move the C9 shape up two frets, to x-5-4-5-5-5), Gmaj7. Then play the plain version (Am, D, G) and compare. Same harmony, much richer colour.

Do these in order. Each one is small. Tick the ones you have practised.

• 1.Extend the chord

  4 min

  1. Play C, then Cmaj7, then Cmaj9. Listen to how each adds colour without changing the chord's role.
  2. Play C7, then C9 (x-3-2-3-3-3). The 9 sits on the high e string.
  3. Play C, then C6. Compare C6 with Cmaj7: both are major, but the 6 is sweeter and more old-fashioned.

  You have it when

  • You can play each pair cleanly and say which note was added.
  I practised this one

• 2.Dominant colours

  4 min

  1. Play G7 (open), then G13 (3-x-3-4-5-x). The 13 is the E on the B string.
  2. Play A7, then A7sus4. The 4 (D) replaces the third: this is the guitarist's 11th chord.
  3. Play E7, then E9. The F♯ on the high e is the 9.
  4. Play each pair again with your eyes closed and name the extension you hear.

  You have it when

  • You can tell the plain dominant 7 from the extended version by ear.
  I practised this one

• 3.An extended ii-V-I

  5 min · 60 → 72 BPM

  1. Play a plain ii-V-I in G: Am7, D7, Gmaj7.
  2. Now replace D7 with D9: the C9 shape moved up two frets (x-5-4-5-5-5).
  3. Loop Am7, D9, Gmaj7, Gmaj7, one bar each.
  4. Finally, try Em9 for one bar before Am7, to lead into the progression.

  You have it when

  • The progression flows at 60 BPM and the extended chords sound clean.
  I practised this one

Untimed while learning the shapes. For the progression, 60 to 72 BPM with one chord per bar and gentle strums.

• Trying to play every note of a 13th chord. A 13th chord has seven notes and the guitar has six strings. Keep the root (or let the bass play it), the 3rd, the ♭7 and the extension; leave out the 5th, and usually the 9th and 11th.
• Adding an 11 to a major chord with its third. The natural 11 clashes with the major 3rd. On dominant chords use 7sus4 (no third); on minor chords, m11 works fine.

Extended chords are a fast way to make a simple progression sound sophisticated. Funk often vamps on a single 9th chord; soul ballads use maj9 and m9 for warmth. Take a progression you know and replace one chord with an extended version.

Short version (10 minutes)

Learn C6, Cmaj9, C9 and G13, and compare each with the plain chord.

Standard version (about 30 minutes)

Do all three exercises, then rewrite a four-chord progression of your own using at least two extended chords.

• Stack thirds past the 7th: 9, 11, 13 (the 2, 4 and 6 an octave up).
• A 6 chord adds the 6th to a triad, without a 7th.
• On guitar, keep 3rd, 7th and the extension; drop the 5th and often the root.
• 7sus4 is the playable dominant 11th.

You are ready to move on when you can honestly say:

• I can explain where the 9th, 11th and 13th come from.
• I can play C6, Cmaj9, C9, E9, Em9, A7sus4 and G13.
• I can use extended chords in a ii-V-I progression.