Chord Extensions and Implications

• omg SDPC Extension reference (joke)
• chord extensions are basically anything beyond 7+ notes in a chord, they're there to give a chord more flavor without altering the core sound.
• Helpful resources: https://old.reddit.com/r/musictheory/comments/hjd0dj/most_things_you_should_know_about_chord/

The safe chord extensions

• Major 7s:

  • 9 is safe
  • #11 is safe
  • 6/13 is safe.
  • Conclusion: Stacking a major chord on the second of the major 7 is safe. (and sounds beautiful!)

• Minor 7s:

  • 9 is safe
  • 11 is safe
    • b11 converts the chord into major 7. So no.
  • 13 is safe.
  • Conclusion: Stacking a minor chord on the second of the minor 7 is safe.

• Dominant 7s:

  • Honestly, do whatever the hell you want it's already dissonant. I don't care.
  • There IS a chord called Hendrix chord, though: It's 7#9, so if we use that.
  • #9 is kul
  • 11 is whatever
  • 13 is whatever
  • Conclusion: Stacking a Dimsus2 chord (wtf) is kul

6th vs 13th

• A 6th chord is not the same as 13th because it's special.
• Although Add6 is technically the same as 13...because the 6th doesn't include the 7th. yeah honestly that's it.

9/11 th Chords

• You might be able to think of sus chords quickly, but you might stagger when thinking of 9/11ths!
• So, as a first exercise, let's map 9/11th to sus chords!
• Then you can memorize from there

13th chord scales

• A 13th chord implies every note in a scale is used! It's easier to remember it as a scale and adjust accordingly.
• Here are some "commonly" used ones. They are commonly used because they just.. make sense and harmonize with the scale.

Chord Symbol	Constructed scale	Note
C △13	C Major scale
C △13 #11	C Lydian Scale	This is a major-y a major chord can get
C 13	C Mixolydian	This is a groovy and mixolydian chords get
C -13

• Another way to think of 13ths is think of 9th as manor chord starting on 2nd.

What about playing it?

• Throw away the fifth. You almost never need it.
• If someone says play a 13th. It usually means play a 13th without the 9th and 11th
• If you want to add a 9th in, do it if you'd like, it's really just there for funsies. 9th is the safest extension and you can always add it in.
• The 11th is the neglected child... until its not.

---

Chord Implications

• An extended chord or slash chord is another way to show how to play a chord quickly.
• The extension is ironically quite important, otherwise they wouldn't be writing it since you would just be adding it when you feel like it.

Major 7ths

• Majors 7ths are usually played as-is
• CM7#11: This is the standard Lydian chord.

Dominant 7ths

• Dominants are often used as the "default" chord if the 7th doesnt matter, but the extension
• C7flat13 chord: Play an augmented C