A turnaround is a brief progression, usually lasting one or two bars, placed at the end of a section or chorus to steer the music back to the start. Its job is to avoid the static feeling of simply holding the home chord. A classic turnaround in C is I–vi–ii–V: Cmaj7–Am7–Dm7–G7, after which the tune begins again on C. Common variants replace chords with dominant sevenths (E7–A7–D7–G7) or with tritone substitutions, giving a chromatic line such as E7–E♭7–D7–D♭7.
Turnarounds appear in the last bars of the 12-bar blues and at the end of most standards, and soloists use them as signposts to know where they are in the form. A loop built on a turnaround never quite comes to rest because it always points back to its own first chord, which is exactly why the shape works so well for the endless, circular grooves of jazz lo-fi.