Conscious control of volume and timbre across different parts of the song — from whisper to scream, dark to bright color.
Sing the same phrase five times: whisper, piano, mezzo-forte, forte, near-scream.
Dynamics are the simplest tool for creating an emotional arc. Whisper = intimacy. Scream = release.
Billie Eilish — 'When the Party's Over': whisper in verses, crescendo into the chorus.