In bar 4, instead of the simple V–I root motion in the original blues, the ii chord of the B7 (Cm) is included so that the measure is even more directed toward the following downbeat with the B7. In bars 8-10, instead of leading back to the tonic with the standard V–IV–I (blues cadence), a series of applied ii–V–I progressions is used to first lead to Gm, which then itself is reinterpreted as a ii and used to lead back to F7 through its own V, which is C7. In the last bar (the "turnaround"), the same type of substitution is used as that in bar 4. In practice, musicians often extend the basic chords shown here, especially to 7ths, 9ths, and 13ths, as seen in this example: