In jazz, a turnaround is a passage at the end of a section which leads to the next section. This next section is most often the repetition of the previous section or the entire piece or song.
The turnaround may lead back to this section either harmonically, as a chord progression, or melodically.
Typical turnarounds in jazz include:
Turnarounds typically begin with the tonic (I) (or a tonic substitute such as iii) and end on the dominant (V7), the next section starting on the tonic (I). They may also end on ♭II7 (which is a dominant substitute). Thus when used in a twelve bar blues pattern, the twelfth bar may end on the dominant. All of the chords in a turnaround may be seventh chords, typically dominant seventh chords for major chords and minor seventh chords for minor chords (e.g., ii7).
Sometimes, especially in blues music, musicians will take chords which are normally minor chords and make them major. The most popular example is the I–VI–ii–V–I progression; normally, the vi chord would be a minor chord (or m7, m6, m♭6 etc.) but here the major third allows for a more interesting modulation. Take the example in C major: C–A–D–G(7). The third of the VI chord (in this case, C♯) allows for chromatic movement from C (the root of I) to C♯ (the third of VI) to D (the root of ii).