Turnaround

A turnaround is a short chord sequence, typically over the last two bars of a blues progression, whose job is to lead the ear back to the start of the next cycle rather than conclude the progression for good. It creates tension that logically calls for a return to the first chord.

A relaunch, not a conclusion

Unlike a perfect cadence that closes off a phrase, a turnaround is built to never really stop: it's a joint between two passes of the progression, not an ending in itself — which is why the same turnaround can repeat bar after bar on a looped blues without ever sounding like a premature ending.

The sheet blues turnaround — E isolates this characteristic sequence.