A turnaround replaces a period of what might otherwise be static tonic harmony with a circle of 4ths. This will often occur at the end of a section, and introduces the first chord of the next section by preceding it with its dominant. This may be, in turn, preceded by a number (typically 0 to 3) of chords from the circle of 4ths.
See paradigms on circle of 4ths.
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