Extended Chords: 9ths, 11ths, 13ths

Stacking thirds past the 7th

Harmony is built by stacking thirds. A triad is three notes a third apart; add another third and you get a seventh chord; keep going and you reach the extensions. The ninth is a third above the seventh, the eleventh a third above that, the thirteenth one more. Go past the thirteenth and you are back to the root, so the thirteenth is the tallest chord there is, every note of the scale stacked at once.

That means extensions are not new shapes to memorise from zero. If you can already play a dominant seventh, a ninth is that chord plus one note. Build up from the sevenths you know and the tall chords stop being scary.

Stack an extended chord, one third at a time

Pick a root, then climb the stack. Watch each extension add a note to the seventh chord underneath it.

This shows the full theoretical stack. In practice, players drop the notes that add least, usually the fifth, often the eleventh, to keep the chord playable with two hands.

What you can leave out

Here is the secret that makes extensions practical: you almost never play all the notes. A seven-note chord will not fit one hand cleanly and sounds muddy anyway. The notes that carry the chord's identity are the third (major or minor), the seventh, and the top extension you are naming. The fifth adds little and is the first to go; the eleventh often clashes with the third in dominant chords and gets dropped or sharpened. Keep the flavour notes, ditch the rest, and a scary 13th becomes four or five comfortable notes. This is exactly the thinking behind rootless voicings.

Extensions across the three seventh families

Each extension comes in dominant, major and minor flavours, following the seventh underneath it. A maj9 sits on a major seventh and sounds lush; a min9 sits on a minor seventh and sounds smooth and soulful; a dominant 9th or 13th keeps the bluesy pull of its seventh. If you play from lead sheets or jazz charts, this is the vocabulary that stops you quietly downgrading every C13 to a plain C7.

Practise extended chords in the game

Get your sevenths solid first, then open the game and build a Custom pool of extended chords, the dom9, maj9, min9 and the 11ths and 13ths are all in the chord database. Play each on your MIDI keyboard or into your microphone and get told instantly whether the shape was right. Add one extension family at a time so the new colour has room to sink in. Free in the browser, nothing to install.

Common questions

What are extended chords?

Extended chords keep stacking thirds past the seventh, adding the ninth, eleventh and thirteenth. A C13 in full is C E G Bb D F A. They add richness and colour beyond a plain triad or seventh, and are the everyday vocabulary of jazz, soul, funk and gospel.

Do I have to play every note of an extended chord?

No, and usually you should not. A 13th chord has seven notes, more than one hand covers comfortably, so players drop the ones that add least, often the fifth and sometimes the eleventh. The essential colour notes are the third, the seventh and the top extension itself.

What is the difference between a 9th, 11th and 13th?

How far up the stack you go. A ninth adds the note a third above the seventh, an eleventh adds another third on top of that, and a thirteenth adds one more. Each includes the ones below it in theory, so a 13th implies the 9th and the 7th beneath it.

How do I practise extended chords?

Add them gradually once your sevenths are solid. In ChordRunner the extended types, dom9, maj9, min9 up through the 13ths, are all in the chord database, so you can build a Custom pool and drill them on a MIDI keyboard or through your microphone with instant feedback.