Jazz is a musical style which cannot be summarised with just the word, 'jazz'. It has so many sub-categories and fusion styles nowadays that the word just hints at the type of audience, rather than the type of music. For the purposes of this Entry, the term refers to the sort of techniques used in all forms of jazz, post-bop.
A good place to start a jazz harmony is with the 12-bar blues. Blues is the foundation of a lot of Jazz and indeed, a lot of other musical styles. Chuck Berry was the first to use this in pop and this swiftly led to the whole rock 'n' roll movement. So it is with jazz. Here is an example of simple 12-bar blues :
Harmonising this is fairly simple using the main major modes. The major modes are the scales you get when you play the same scale (eg C major), and start in on a different note (eg C major played from D to D, the Dorian Mode). Here is a list of the major modes in a harmonised C major scale.
|Chord||Start/End Note||Mode||Tonality||Played over|
|1||C to C||Ionian||Major||Major or M7 chord|
|2||D to D||Dorian||Minor||Minor or m7|
|3||E to E||Phrygian||Minor||Minor|
|4||F to F||Lydian||Major||Maj7|
|5||G to G||Mixolydian||Major||Dominant 7, 13 or 9|
|6||A to A||Aeolian||Minor||Minor|
|7||B to B||Locrian||Minor7b5||m7b5 or diminished|
The way we put this into context is to play a certain scale, when we get a certain type of chord. This is also described above. This isn't just the case for jazz, but for a lot of classical and pop music. Jazz harmony uses all sort of scales and chords that are rarely found anywhere else in popular music. These are chords and scales related to the melodic minor and the harmonic minor family of harmony. For those of you already fed up with learning theory behind it, here is a jazz 12-bar to practice and give you an idea of what you are getting yourselves into.
|4/4||Bb13||Eb9||Bb13||Fm9 Bbalt||Eb9||Edim||Dm7||G7b9||Cm7||F7#9||Bb9 G7||Cm7 G7#9|
Now, there are some true jazz chords there. Using the same theory we used to create the major scale modes, we can create modes from the melodic minor scale. The next scale we will look at is the seventh mode of the melodic minor scale, which means that it starts and ends on the seventh note of the scale. So if we were playing C melodic minor, we play it from B to B.
The scale we have created is the superlocrian. It has a very distinctive sound and can be heard in many pieces of jazz. Its main use is over an altered dominant seventh chord. For example, in the above sequence, it would be used on the last chord, G7#9. and also the two chords G7b9 and F7#9. Here we would use G superlocrian and F superlocrian, respectively. Now what we have to do is apply the scales to the appropriate chords, and we have nailed the harmony. Here we go. This is one way to harmonise the sequence using the methods described.
|4/4||Bb mixolydian||Eb mixolydian||Bb mixolydian|| F Dorian
|E diminished||D Dorian||G superlocrian||C Dorian||F superlocrian||Bb mixolydian G mixolydian|| C Dorian
Now, get out there and find your own sequences to harmonise! That way, you will learn how to understand jazz and the harmony surrounding it.