We begin by looking at the changes the soloists improvise over (Example 1). It is a 12 bar Blues structure with a little “unbroken II-V chain” (Link) beginning at bar 8. The head is also fundamentally a 12 bar Blues in ‘C’. It’s an Advanced Form (Link), with chromatic movement at bars 2, 6 and 9.
Example 2 shows the song’s bass movement with “resolution” points at bar 4, 8 and 12.
The little three bar “bridge” beginning on bar 9 is particularly interesting. The chords are indeterminate. They can be seen as triad stacks – an Am triad with a Em triad on top. The first chord could also be called a Am7 9 11. But what makes the chords indeterminate is the lack of a third in the lower triad.
The chords are most interesting when compared to the Unbroken II-V Chain in Example 1. The chords seems to be a compression of the soloing changes. Bar 8 is an Em7 going to an A7. The chord in Example 3 is an Em7 on top of an A chord!