Recommended Reading
This article is written with the assumption that the reader has at least a small working knowledge of basic musical theory terms such as interval, triad, chord, scale etc. If you are unsure of meaning of these terms then is is possible to look them up using an online musical dictionary such as this one: http://www.classicalandjazz.co.uk/Dictionary/
One of the most common misapprehensions about jazz is that it is 'random', that the musicians are all voicing their own ideas completely independently to one another. In fact, despite many years of trying to convince her otherwise, my own mother is still convinced that jazz is 'widdly' music which 'makes no sense'. That's right, she uses the word 'widdly'.
There are some instances in which one might argue that jazz can be completely free and random – that type of jazz was cleverly named 'free jazz'.
Most jazz however abides to a much more clearly defined structure. Since the days of young Louis Armstrong and Tin Pan Alley right through the swing era, bebop, cool, fusion and all the other numerous stratifications which form the huge oeuvre of this great music there is one prevailing method – the 'head' arrangement. The 'head' of the tune incorporates the melody over the changes (chords). Once the head is finished i.e. once the song has finished one cycle, the musicians go back to the beginning of the form and begin reinterpreting the melody and the chords to form solos.
At this point it is clear why people struggle to hear the difference between complete chaos and organised chaos. The musicians have outlined the structure of the song and have begun to interact, even musically converse, over a reinterpretation of the song. The skeleton of the song, however, remains rigidly in place. This skeleton is formed from the ever-present changes. Although they may be voiced differently, the changes provide a unification and a direction for the soloists and their accompanists.
There are, of course, exceptions to all of these guidelines but for the sake of clarity and brevity I'm focusing on the most common methods.
The two most common structures which jazz composers have relied upon are the '12-bar blues' and 'rhythm changes'.
The 12-bar blues is a musical form which pre-dates jazz.
The chords in a generic blues:
I I I I7
IV IV I I
V VI I V7
Normally in jazz musicians use a II V I 'turnaround' towards the end of the form, particularly if playing in a minor key:
I I I I7
IV IV I I
II7(b5) V7 I V7
Of course there are many variations on the timeless form.
Rhythm changes is more or less based upon the chords of George Gershwin's 'I Got Rhythm'. It was used extensively by musicians in the bebop era to produce new tunes.
Rhythm Changes:
A section:
I VI II V
I VI II V
I I7 IV #IVdim
I V I I
B section:
III VI7
II7 V7
Rhythm changes uses a very traditional AABA structure.
With a basic understanding of those two structures among others the listener can begin to really hear the intricacies of the tunes and what the soloists are trying to achieve. The music begins to feel less random and more exciting and relatable.
