The two previous riffs are commonly used in what is known as stop time. This involves the band playing a repeated riff with regular stops as part of the pattern. Either the singer or the soloist can play in the gaps between the stops.
In the following solo, the band plays stop time for the first four bars and the harmonica plays a response in between each stop. In the fourth bar, the whole band plays a buildup which leads to the groove used for the rest of the progression. The groove used here was made famous by Muddy Waters in his song "Hoochie Coochie Man". This solo also features grace notes (indicated by a w above the indicated note. Grace notes are explained in detail on the following page.