I know most of you don't play jazz, but I've learned a #### ton of information this last year and thought I might share some of it with you guys for free so you don't have to pay a fortune for it like I have. A lot of it is dense and won't make any sense to you unless you've got a basic hold on simple theory concepts. For those of you that do, I know tragic does, hopefully this will be of some interest.

Here's some jazz chord theory.

To begin I'll explain the most basic categories of chords and their functions in tonal western music. Chords essentially only have two major functions, to create tension and movement, or to resolve tension and movement. Chords that create or build tension fall into two types, either subdominant (or predominant) and dominant. The chords that resolve tensions are called tonic chords (or possibly post-dominants).

With this in mind, it's helpful to realize what the chord you're using at any given moment's function actually is in context. Is it creating tension, or is it resolving tension.

Subdominant type chords tend to lead either to dominant, or back to tonic directly. Dominant chords almost invariably lead back to tonic, though sometimes they make different stops on the way, when one plays a dominant type chord, one is invariably moving somewhere, usually back to tonic.

Tonic chords can include any major or minor chord, subdominants are almost always major or minor but are also sometimes substituted by half-diminished and even dom7 chords. Dominant chords are of course dom7 chords and also substituted by diminished and augmented chords. Suspended chords can often act as all three depending on how they are being used.

So using the diatonic chord scale for C Major...

I-C

ii-d minor

iii-e minor

IV-F

V-G

vi-a minor

vii-b diminshed

...we would begin to understand how functional chord progressions work.

C is the true tonic chord of the key, F is the true subdominant chord, and G is of course the dominant. All of the other chords then are only acting as substitutes for one of these three chords. This is why the I IV V is the most essential progression. Another big chord progression is the I vi ii V progression in major and minor. This works so well because the vi chord is a strong substitute for the I chord as it has two of the same notes in common. The ii chord acts great in substitute of the IV chord because it also has two notes in common. Because the vii chord has the leading tone or 7th scale degree, is diminished in nature and needs resolution, and has two notes in common with the V chord, it is an excellent substitute for the Dominant chord.

And so on, any chord that has two or more notes in common with another chord is usually a good substitute for that chord.

Also, certain patterns of chord progressions are also common. Moving down the scale back a third is very common, also moving around the scale back in 4ths or 5ths yields many musical ideas. Moving up the scale in 2nds, 4ths, and in 5ths is especially common. Moving up in thirds sounds very musical as all the chords will share the two-note in common rule.

Extended Harmonies in Jazz:

When taking tertian harmony beyond the octave (tertian means third harmony) there are certain rules to how chords are built: i.e. avoid doubling tri-tones in chords (the interval between the 4th and 7th of the major scale): in major chords the 11 is often raised, which is the same as a #4 or Lydian mode. In minor chords, for the same reason, the 6th is also raised which is the same as the 13th or Dorian Mode.

Built from Lydian Mode

Maj7#11--1 3 5 7 9 #11

Maj13--1 3 5 7 9 #11 13

Built from Dorian Mode

Min11--1 3 5 7 9 11

Min6 or Min13-- 1 3 5 6 7 or 1 3 5 7 9 11 13

Built from Harmonic or Melodic Minor:

MinorMaj7: 1 3 5 7

On dominant chords, in jazz, even in major keys, you can borrow dominant chords from other modes. For example, the IV V and VII chords of a melodic minor scale are all technically forms of Dominant 7th chords, in harmonic minor the V chord is the only dominant 7th chord.

So you could build a dominant chord from a melodic minor starting on the fourth mode, which is called Lydian dominant because it is essentially a lydian scale with a flat 7th. The chord often built from this mode is:

Dom7#11- 1 3 5 7 9 11 (built from lydian dominant)

The chord built from the fifth mode of melodic minor, or mixolydian b6, is often:

Dom7b13-1 3 5 7 (9 and 11 optional) b13

The chord from the 7th mode of melodic (superlocrian mode) is often just called the Alt chord:

Altdom or Dom7alt or just Alt: 1 3 5 7 9 11 13 (built from superlocrian)

From 5th mode of harmonic minor you could have a few chords but mainly it works the same as the above:

Dom7#5 or Dom7b 13: 1 3 #5 7 or 1 3 5 7 13

This is probably very confusing because I'm using a relative approach to chord formulas instead of a parallel, in other words I'm comparing the scale degrees of the chords from the modes they derive from instead of their relation to the major scale. I did this to avoid a plethora of b9 #9s, #11, etc. but that's actually perhaps an easier way for some of you to grasp these concepts so I'll explain the above that way now.

If I were to build a fully extended chord from the Major scale starting on tonic or the root, it would look like this:

1 3 5 7 9 #11 13

The reason the 11th is raised is to avoid doubling the tritone of the scale which occurs between the 7th and the 4th of the major scale.

If I built a fully extended minor chord with a parallel relation to the major scale it could look a few different ways.

1 b3 5 b7 9 11 #13

In this case the 13th or 6th is raised to avoid the doubled tri-tone.

1 b3 5 7 9 11 #13

In this case the Major 7th is retained, giving a very unstable dark sound called the minMaj7th chord, which would have been harmonized from a melodic or harmonic minor.

If I were to build a fully extended dominant chord in a parallel relation to the major scale it would look like this:

1 3 5 b7 9 11 (or #11) 13

Again you may raise the 11th or 4th but is not necessary on a fully extended dominant chord.

Now dominants may be altered in a number of ways by raising or lowering the different extensions, the general rule, however, is only alter the 5th, 9th, 11th, and 13th. The 3rd and b7th must not be altered in anyway as this is what gives the dominant chord its quality. As a result a number of possibilities occur, I will organize them in relation to the 5th scale degree in three families, in reality you could just as easily organize them by any of the scale degrees that are altered but I will not. The 13th is only ever lowered as raised it merely becomes the b7 enharmonically. The 11th is not raised on b5 dominants as a #11 is the same enharmonically as a b5. Likewise the 13th is not lowered on #5 chords or augmented chords because they are the same scale degree enharmonically.

The natural 5 family:

1 3 5 b7 9 11 13

1 3 5 b7 9 11 b13

1 3 5 b7 9 #11 13

1 3 5 b7 9 #11 b13

1 3 5 b7 b9 11 13

1 3 5 b7 b9 11 b13

1 3 5 b7 b9 #11 13

1 3 5 b7 b9 #11 b13

1 3 5 b7 #9 11 13

1 3 5 b7 #9 11 b13

1 3 5 b7 #9 #11 13

1 3 5 b7 #9 #11 b13

The b5 family:

1 3 b5 b7 9 11 13

1 3 b5 b7 9 11 b13

1 3 b5 b7 b9 11 13

1 3 b5 b7 b9 11 b13

1 3 b5 b7 #9 11 13

1 3 b5 b7 #9 11 b13

Finally, the #5 or augmented family:

1 3 #5 b7 9 11 13

1 3 #5 b7 9 #11 13

1 3 #5 b7 b9 11 13

1 3 #5 b7 b9 #11 13

1 3 #5 b7 #9 11 13

1 3 #5 b7 #9 #11 13

Now many of these dominants can be built from multiple modes, as a result multiple modes are options to draw from for melody notes over any of these dominants.

Now where things get tricky, or untricky. In jazz music, and most popular music, aside from the majority of classical, rock, folk, and country music that is very triadic and avoids extended harmonies, all of these dominants are interchangeable. Meaning hypothetically, anytime there is a dominant chord in a song, any of the above dominants could substitute in it's place. Now depending on the chord you're resolving to some choices will sound better than others. For example, dominants derived from minor modes tend to sound best resolving to minor type chords, and dominants derived from major chords tend to sound best when resolved to major chords. However, if one want to add extra tension, building up to an even greater resolution on the resolving chord after the dominant, then substituting a borrowed or "out" dominant type chord adds quite a bit of interest.

One more thing about dominants, a tri-tone is the interval a #4 or b5 away from any note. So for the note C the tritone is F# or Gb. Now say for example I had C Dominant chord of sometype and I wanted to alter it in someway. Their are of course, as you've just seen, a number of ways to accomplish this, but one way used commonly in Jazz, R and B, Gospel, Soul, Funk, and even in blues, has to do with this tri-tone thing.

If I take a C dominant 7th:

C E G Bb

and instead play a dominant chord a tritone away, so Gb dominant, it looks like this:

Gb Bb Db Fb

Now remember that two note in common rule from earlier? If I look at the Gb dominant it at first only seems to have one note in common with C dominant, the Bb. However, the Fb is enharmonically the same note as E natural. So there's our two notes in common. And further, remember the rule about altered dominants? It's okay to alter any note of the chord except the 3rd and b7th. In this case the 3rd and flat 7th of C are E and Bb. The 3rd and b7 of Gb are Bb and Fb (or E), which is exactly the same just reversed. Since all we really need for the dominant sound is the 3rd and b7th, then playing any dominant chord of any type or alteration a tri-tone away is from the actual dominant chord implied is always a possibility for alteration.

This is called Tri-tone substitution, and can be used on any and every single dominant type.

Try it out!

I know most of you don't play jazz but if you read through this once or twice you may get a lot of fresh ideas for diatonic harmony.

Next time I'll explain some methods for writing "outside" the box and modulating to new keys, and then I'll hopefully get around to explaining some modal theory and maybe quartal harmony.

A nice diatonic chord progression to play over where you can start applying some of these ideas would be a tune like Autumn Leaves. It's made up of primarily ii-V-I progressions tied together, which is a very strong subdominant-dominant-tonic relationship. It also gives a few opportunities to try out extending harmonies and tri-tone subs.