How do cadence and the return of a key help create a sense of musical conclusion?

In music, the sense of conclusion is primarily achieved through the interplay of harmonic tension and resolution, which is structured by cadences and the return to a tonic key.12

The Role of Cadence

A cadence serves as a musical "punctuation mark," signaling the end of a phrase, section, or movement. In tonal harmony, the most definitive sense of closure is provided by the authentic cadence, where a dominant chord (V) resolves to the tonic chord (I). This progression is powerful because the dominant chord contains a "leading note"—a pitch only a half-step away from the tonic—which creates a strong harmonic pull toward the home key. Conversely, a half cadence ends on the dominant, leaving the listener with unresolved tension that implies the music must continue.342

The Return of the Key

The return to the tonic key is essential for establishing structural unity. In forms like the sonata, a movement often explores various keys, creating tension through modulation. The recapitulation acts as a psychological resolution, where themes previously heard in contrasting keys are reconciled by being restated in the tonic. This return provides a sense of equilibrium, effectively "coming home" after the harmonic journey, which is often reinforced by a final, definitive cadence.5167