Modulation changes the tonal center mid-song; the dominant seventh of the new key is the primary agent

Modulation is a deliberate change of key within a piece of music. The most effective modulation route uses the dominant seventh of the target key: the ear only registers a true key change when it hears a perfect cadence (V7-I) in the new key. Without this cadence, the ear perceives only a temporary shift (a tonicization). Common modulation targets: the relative major/minor (same key signature, smoothest change); the dominant key (one sharp more); the subdominant key (one flat more). The cycle of fifths shows the most closely related keys.

Examples

C major to G major: establish G7 (G B D F), then resolve to G major. C major to A minor: no accidentals needed (relative pair).

Assessment

Plan a modulation from D major to B minor in 4 bars. Which chord signals the new key? Identify the dominant seventh of B minor.