Half cadence
A turn that stays on the dominant — open, questioning, not finished.
What it means
A half cadence (German Halbschluss) is a cadence that ends on the dominant. It closes a section but not the music: the dominant demands the tonic, and this expectation remains open. The impression is that of a colon or a question — the continuation is compelled.
Musical use
Various sonorities lead to the dominant, most often the tonic, the subdominant, or the double dominant; often a cadential six-four chord precedes it, delaying the dominant. The dominant itself in a half cadence usually stands in root position and without seventh, because the seventh would push the sound too strongly toward resolution and make it harder to stay put.
In the articulation of form, the half cadence is the counterpart to the full close. In the period it concludes the antecedent, while the consequent answers with a full close — question and answer. In larger forms it often marks the end of the transition before the second theme: the music stays on the dominant of the new key, often prolonged and with emphasis, and thus prepares the entry.
A special form is the Phrygian cadence, a half cadence in minor in which the subdominant in first inversion leads with a semitone step in the bass downward to the dominant.
The half cadence is to be distinguished from the deceptive cadence: with the half cadence the music stays on the dominant; with the deceptive cadence the dominant leads on, but not to the tonic but to a substitute.
The half cadence is the most important means of letting a phrase end open. Frequent paths to the half cadence lead through the subdominant or through the double dominant. Before recapitulations and closing sections, the dominant of a half cadence is often held long so that tension grows before the return to the tonic.
Performance practice
Keep the tension at the half cadence up instead of releasing it — a half cadence that sounds like an ending misses its effect. Do not take the dominant sonority back, and leave the pause after it active, as expectation. And, when shaping, distinguish it distinctly from the full close, which usually answers it a few bars later.