This is as close as we get to jazz in this section, this is in the style of 1960s modal jazz which became popular in the late 1950s and 1960s. perhaps it was a backlash against the complexity of bebop.
In this type of jazz there is often only one chord, or a vamp, which can last for a long time. We are not going to modes in too much detail here, you can read about them on the Modes in Improvisation Article. In this context we think of a mode as being a scale which appears to be the same as a normal major scale, but starting on and having a different note as its “home.” In this case we are looking at one of the most common in many popular styles, the Dorian. It is like a major scale, but starting on the second degree, so a D Dorian has the same notes as C major. (You may already have noticed that the natural minor is a mode – it is in fact the Aeolian and has the same notes as a major scale but based around the sixth degree.)
The great thing about this is that (as with the Gorilla vamp exercises) we do not even have to think about chord changes, we just concentrate on using the scale to make some interesting melodic improvising. You may notice that the piano is playing more than one chord, but you needn’t worry about following them, because the bass line is implying just one root (around a C in concert pitch)
First of all you can try just running up and down the scale, or use shorter sections, to get used to it. However after a while you should be able to jump between the notes. You don’t have to stick exactly to the dorian mode, you’ll find that a pentatonic or blues scale will also fit nicely.
For Eb instruments the scale is A Dorian = A B C D E F# G A
For Bb instruments the scale is D Dorian = D E F G A B C D
(NB: to be edited. Intro = 1 x vamp and 2 bar drum break)