In this follow-up lesson to “Triads and 7th chords“, chordal extensions and alterations (to dominant chords) will be explained. By the end of this lesson, you should be able to decipher most jazz chord symbols.
As we know, most chords are typically built by stacking thirds. If we continue to stack thirds beyond 4 notes, we enter into territory beyond the octave. These notes are called extensions. Chordal extensions are easily explained using this equation:
9 = 2
11 = 4
13 = 6
Alterations to Dominant Chords:
9ths and 5ths are often altered (lowered or raised) on dominant chords resolving to their corresponding I chord. Altering the 9 and/or 5 adds color to the chord and generates more tension and chromatic pull towards its resolution.
Altered 9ths: b9, #9
Altered 5ths: #5 [enharmonically labeled b13] and b5 [enharmonically labeled #11].
Most of the chord symbols one will encounter in “straight ahead” jazz contexts are listed and explained on the attached handout, Chord Symbol Notation & Identification. Study this sheet carefully and practice constructing the chords in several keys using the numeric formulas (which always relate to the major scale).
You may wish to create a list of rules and exceptions to rules. Here are some to get you started:
- 9 implies 7.
- 11 implies 9 and 7.
- 13 only applies to dominant chords. Use 6 for major and minor chords.
- 13 implies 9 & b7. It does not imply an 11 or #11.
- For half diminished chords, use b5 and not it’s enharmonic, #11.
- For major chords, use #11 and not b5.
- For dominant chords, #11 or b5 are acceptable.
Homework Practice Assignments:
1) Chord Construction: Every day, construct all the chords on the attached “Chord Symbol Notation & Identification” handout, in 2 keys. Do this in two separate practice sessions. On “day 1”, play through the keys of C and Db. On “day 2”, play through D and Eb, etc.
2) Extensions & Alterations: With 2 stacks of recipe cards, practice identifying chordal extensions and alterations. One stack of cards consists of all 12 chromatic pitches, the other consists of extensions (9, 11, 13) and alterations (#9, b9, #5, b5, b13 and #11). This is a fun game to play with like-minded musician friends.