Her most pronounced vocal tweak is on “Wildest Dreams,” a sweaty and dark tale of dangerous love. In the verses, Ms. Swift sings drowsily, as if seducing or just waking up: “I said ‘No one has to know what we do’/ His hands are in my hair/ His clothes are in my room.” Then, at the bridge, she skips up an octave, sputtering out bleats of ecstasy, before retreating back under the covers.