What Are Tensions? 9 · 11 · 13, the Rainbow of Jazz Harmony

In Part 5 we stacked one more third on the triad to build a seventh chord. But a question sneaks in: do we really have to stop stacking thirds at the 7th? What happens if we add one more, and then another? Keep climbing and you reach today's protagonist: tensions (9 · 11 · 13).

Why not stop at the 7th?

The recipe is the same as ever. On top of do-mi-sol-ti (the seventh chord), keep skipping a step and adding a note, and re, fa, la rise up in turn. But re is the 2nd — so why call it a 9? The chord already uses everything up to the 7th, so any note above that is counted as landing an octave higher. The 2nd an octave up becomes the 9th, the 4th becomes the 11th, the 6th becomes the 13th. We skip 8, 10 and 12 because those seats already belong to the root, 3rd and 5th.

So a tension isn't a newly invented note. It's simply a note that was already in the scale, met again an octave higher. Because it sits at the very top of the chord, far from the root, it tints the whole harmony with a soft glow.

9, 11, 13 — colors an octave up

Add the layers one at a time and you can hear the color spread. Put a 9 (re) on the cozy Cmaj7 and Cmaj9 opens up, brighter and more airy. Add the 13 (la) on top and Cmaj13 blooms wide open — that shimmering chord of city pop and jazz ballads. If a seventh chord was a subtle nuance laid over bright/dark, tensions are the paint that turns up the saturation one notch at a time.

Can you add any note? — the avoid note

You can't just pile on any tension you like, though. Put a natural 11 (fa) on a major chord and something clashes and turns muddy. Fa sits a semitone away from the 3rd (mi), rubbing against it and clouding the chord's bright face. A note that dirties the color like this is called an avoid note. That's why major chords usually drop the 11 or raise it a semitone to #11. (On minor and dominant chords the 11 behaves differently — each chord has its own set of tensions that fit.)

A tension isn't dissonance — it's seasoning

Here's a common misunderstanding to clear up. A tension isn't a "dissonance" — it's closer to seasoning. Choose a fitting tension and add it in the right measure, and the sound doesn't get noisy; it just gains one more coat of color. The lushness of a ballad, the polish of jazz, the languor of R&B — most of it comes from these tensions. If the plain triad is a single crayon, a tension is the wash of watercolor that repaints the same picture.

Reading chord symbols, one layer up

Just add the tension notation to Part 5's rules. Cmaj9 is a major 9, a bare C13 is a dominant 13, and when you want color while keeping the 3rd you write Cadd9. A note raised to dodge an avoid is written in parentheses, like Cmaj7(#11). When a chart says Dm9 - G13 - Cmaj9, you can now read just how brightly each chord has been painted.

🎹Hear the rainbow yourself — open the “Tensions” lesson in Theory Lab→

Tensions are the world of color that begins at a chord's fifth layer and up. Over the bright/dark of a triad and the nuance of a seventh, 9 · 11 · 13 add saturation, and as long as you dodge the avoid note, that color is seasoning, not dissonance. Next time we turn slightly and ask what happens when you remove the 3rd entirely — into the suspended chords of sus and add. New to chords? Start with Part 3: What Is a Chord? and Part 5: Seventh Chords.