Jazz harmony is unmistakably rooted in the tradition of music theory. It relies on melodies that are harmonized with chords. The principal difference between jazz harmony and other harmony is its use of chords that are taller than triads—taller as in vertically, on the page, like the G13 chord shown in FIGURE 13.1.
FIGURE 13.1 G13 Chord
The G13 chord is considered a tall chord because it's tall on the page. It fits into a class of chords called extended chords. To understand extended chords, you need to understand extended intervals. This book's earlier discussion of intervals didn't say much about extended intervals, but jazz harmony requires it. You need to know what a thirteenth really is and what extended intervals are.
By now, intervals should be a common part of your music theory experience. Funny how there's more to learn about them. Intervals have shown you the exact distance between any two notes. Up until now, you have not distinguished intervals larger than an octave. You heard about them, but you never saw them put into practice.
Do a quick review: After you pass the octave (which is also called an eighth), you distinguish these larger intervals with, you guessed it, larger numbers. Any interval larger than an octave is considered an extended interval. However, there are some intervals that are never extended.
Music theory does not distinguish the distance of a third or a fifth differently, no matter what octave it is in. Much of this has to do with historical practice, but the real reason lies in triadic harmony.
Since the majority of jazz chords include extended intervals, just remember the rule of nine in order to decipher what a ninth from C is, for example. In jazz, the seventh chord is the smallest unit you will see, and typically, taller chords are more common than seventh chords, so you'll need to know extensions in order to succeed.
If you start stacking thirds on top of one another, you get this order: C–E–G–B–D–F–A–C. Or as intervals: root, third, fifth, seventh, ninth, eleventh, thirteenth, and root.
Using the rule of nine from Chapter 2, the extended intervals (ninth, eleventh, and thirteenth) spell the same as a second, fourth, and a sixth; they are just an octave away. The reason you don't see tenths and seconds (thirds and fifths) is that when you stack thirds, those intervals simply don't come up. Once you get to thirteen, the next third brings you back to the octave.
The other reason that thirds and fifths are not counted as extended intervals becomes clear when you hear them compared to other intervals (such as seconds versus ninths). To most ears, thirds and fifths sound the same no matter what octave they occur in. This is not to say that they sound identical, but the difference is so minute that you don't need another name for them based on whether they are more than an octave apart. A second sounds very different than a ninth. Try this out on your instrument.
Now that you know about extended intervals, you need to look at extended chords. You learned about four families of chords: major, minor, diminished, and augmented. When sevenths are added into the equation, you get a fifth chord family: dominant chords (major triads with minor sevenths). These basic five chords and their extensions make up the majority of jazz harmony. To get by in jazz, you need to understand major, minor, and dominant extensions first. You will deal with diminished (which is typically note extended) and augmented chords later.
The basic jazz major chord is the major seventh chord. As you recall, a major seventh chord is a major triad with a major seventh interval added to it. In addition to the seventh, you see major chord extensions. Major chords can be written the following ways and still fall under the umbrella of major and, thus, substitute for each other:
C Major 7th
C Major 9th
C Major 11th
C Major 13th
The formula for these chords is pretty simple to spot: root (major) extension. Any chord that follows that formula is in the major seventh family. For example: F Major 9th is a major seventh chord, but F9th is something else because it lacks the necessary major component in its name. Knowing these basic rules will make life much less confusing, as jazz deals with chord symbols more often than actual written voicings. That's right, in jazz, you turn symbols into sounds.
In jazz, all major chord extensions take their notes from the major scale built off the root. A D Major 13th chord will take all of its notes from the D major scale. This is important because the spelling of the individual notes has to follow the home scale or the chord won't sound right. In practice, advanced jazz musicians often alter the notes in very tall chords, but that's a matter of personal taste.
The basic jazz minor chord is the minor seventh chord. As you recall, a minor seventh chord is a minor triad with a minor seventh interval added. In addition to the seventh, you see minor chord extensions. Minor chords can be written the following ways and still fall under the umbrella of minor and, thus, substitute for each other:
C minor 7th
C minor 9th
C minor 11th
C minor 13th
The formula for these chords is pretty simple to spot: root (minor) extension. Any chord that follows that formula is in the minor seventh family. For example: F minor 11th is a minor seventh–type chord, simply extended.
In jazz, all minor chord extensions take their notes from the Dorian scale built off the root. A D minor 13th chord will take all its notes from the D Dorian scale. This is important because the spelling of the individual notes has to follow the home scale or the chord won't sound right. In jazz, the home scale for minor chords is the Dorian mode, not the expected natural minor scale. This is one of the places where jazz starts to pull away from traditional harmony: its use of modes for harmonic and melodic purposes.
The basic jazz dominant chord is the dominant seventh chord. As you recall, a dominant seventh chord is a major triad with a minor seventh interval added to it. In addition to the seventh, you see dominant chord extensions. When used in practice, many jazz players will simply call these chords seventh chords and leave off the moniker dominant as it's implied. Dominant chords can be written the following ways and all still fall under the umbrella of dominant and, thus, substitute for each other:
The formula for these chords is pretty simple to spot: root extension. Any chord that follows that formula is in the dominant seventh family. For example: F11th is a dominant seventh–type chord, simply extended to the eleventh.
Typically, with dominant chords comes chordal alterations. An alteration is some sort of change to the fifth or ninth of the chord. An altered dominant chord may read like this:
Even though that chord looks kind of scary, it's still very plainly dominant because at its core, it's a C7 with other stuff added to the end of it. You will look at this in more depth in the section titled “Substitutions and Enhancements.”
In jazz, all dominant chord extensions take their notes from the Mixolydian scale built off the root. An E13th chord will take all its notes from the E Mixolydian scale. This is important because the spelling of the individual notes has to follow the home scale or the chord won't sound right. In jazz, the home scale for dominant chords is the Mixolydian mode, not the major scale (that's reserved for major seventh chords). This is another example of modal use in jazz.
What about diminished and augmented? Well, in jazz, the diminished seventh chord is very common, and it is written exactly as you'd expect to see it: C°7. The other type of diminished chord, the half diminished chord, is often found in jazz, but it rarely goes by its classical symbol of CØ7. The symbols for full and half diminished simply look too close to each other. To rectify this, half diminished chords are written as “Minor 75” chords, which gets you to the same chord and completely avoids confusion with the other diminished chord. Almost 99.9 percent of the time, you can assume that a diminished chord is a fully diminished seventh chord.
As for augmented chords, they appear as you'd expect them to, in the two varieties you studied in Chapter 8: Cmaj7+ (C–E–G#–B) and C7+ (C–E–G#–B). You can extend an augmented chord, but it's pretty rare. For most things, if you can decipher the major, minor, dominant, diminished, and augmented chord symbols, you're almost there.