Extensions (9ths, 11ths, 13ths)
Remember how we build chords by stacking 3rds? (1 – 3 – 5 – 7). What happens if we keep going?
24.1 The 9th (The Sweetness)
- Stack: 1 – 3 – 5 – 7 – 9.
- What is a 9? It’s just the 2nd note, but an octave higher. (In C Major, the 9th is D).
- Sound: Adds a lush, expensive, “Stevie Wonder” sound to the chord.
- Notation: Cmaj9 or C9.
24.2 The 11th (The Suspension)
- Stack: 1 – 3 – 5 – 7 – 9 – 11.
- What is an 11? It’s the 4th note an octave higher. (In C Major, the 11th is F).
- The Danger: In a Major chord, the 11th (F) clashes horribly with the 3rd (E). So, we usually “Sharp” it (#11).
- Sound: The #11 creates the Lydian “spacey/dreamy” sound (Simpsons theme song).
24.3 The 13th (The Limit)
- Stack: 1 – 3 – 5 – 7 – 9 – 11 – 13.
- What is a 13? It’s the 6th note an octave higher. (In C Major, the 13th is A).
- Sound: Thick, rich, and full. If you play a C13 chord, you are playing almost every note in the scale at once.
- Note: You can’t play all 7 notes with 5 fingers! Jazz pianists usually drop the 5th and the root (the bass player has the root) to make room for the cool extensions.
This concludes the core instructional text of “The Musician’s Master Key.”
You now have the complete roadmap from “What is Sound?” to “Jazz Composition.”