FORMS FOR IMPROVISATION

     Most improvisation is done in one of two basic frameworks:

1.  The 12-bar blues.

2.  The popular song.

     There are other forms, particularly in contemporary improvisation, such as an agreement that improvisation will take place for 16 bars in the Dorian Mode, 8 bars in the Lydian Mode, then 8 bars in the Dorian Mode again. There is even a “free” form, where musicians just start playing and see what happens. But the two main forms cover about 95% of all improvised jazz today, so we’ll take a close look at these two.

12-BAR BLUES FORM

     Nobody knows exactly how the musicians around the turn of the century came to settle on a format for the blues, but at least by about 1914 it was obvious that the blues were generally performed in a 12 measure format which came to be referred to as simply “the blues.” It’s possible to have “blue notes” (flat 3rds, 5ths, 7ths) in any popular song, but when jazz musicians speak of the blues, they mean the 12-bar format.

     Here is the structure of the 12-bar blues:

4 bars of the I chord (the root chord of the tonal center)

2 bars of the IV chord (often with the 7th)

2 bars of the I chord

2 bars of the V chord (almost always with the 7th)

2 bars of the I chord

Then repeat for as many times as desired

     In the key of C, the 12-bar blues would look like this:

     In the key of B flat, the 12-bar blues would follow this pattern:

     Over this chord structure, the musician improvised a melody, based on the given chords and scales of those chords. He is free to play whatever he wants to play, consistent with his ability and taste (his taste to start with – later he will look to other musicians he admires for standards of taste, unless he is extremely inner-directed.)

THE POPULAR SONG FORM

     The other standard form on which improvisation takes place is the popular song. Each popular song has its own distinctive chord progression, plus its own unique melody. In the 12-bar blues for there was only the chord progression structure – no melody.

     Most popular songs fall into one of three categories:

ABA form – theme A, theme B, theme A

AABA form – theme A, theme A, theme B, theme A

ABAC form – theme A, theme B, theme A, theme C

     The largest percentage of popular songs fall into the AABA category, the usual length of the song being 32 bars:

A – 8 bars

A – 8 bars

B – 8 bars

A – 8 bars

     Jazz musicians improvise from the chord structure of the popular song, often making reference to the individual melody in their improvised creations.

     Here is the chord progression structure of one popular song in ABAC form:

     To sum up:

     A pianist has at his disposal all the resources of melody, harmony, rhythm, plus all the variables of dynamics, pitch, tone, and other elements on the tension continuum. With these resources he can create an improvisation over the framework of a popular song or the 12-bar blues. The success he achieves will be proportional to his talent plus his acquired knowledge and willingness to experiment.