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17.2 · The Other Chords

The sweeteners

Stacking a third on top makes a 7th chord, and 7ths add pull. These chords add a note without building a 7th: pure color, no extra tension. Think of them as sweeteners. The triad still does the work, the added note just changes the light.

Three sweeteners on C

A 6th, a 6th on minor, and a 9th floating an octave up. Each one note away from a plain triad.

major triad + a 6th · the old-Hollywood ending: doo-wop and swing tunes close here

minor triad + a major 6th · minor with a curl of smoke: noir soundtracks, gypsy jazz

major triad + a 9th (an octave-up 2nd) · the shimmer: 90s acoustic guitar's favorite chord

Sweetener or 7th?

C6 and Cmaj7 differ by one note (A vs. B) but land differently: the 6th settles, the maj7 hovers. Three endings for the same phrase:

Add 9 vs. sus2: cousins, not twins

Both feature the 2nd/9th, but add9 keeps its third (still major!) while sus2 gave its third away (neutral). Back to back:

Quiz

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What separates a sweetener (6, add9) from a 7th chord?

Score 100% on every quiz and game to complete this lesson.The dark machinery →