Erasure's bubbly brand of Hi-NRG was made for dancing, but there's a softer, sadder side to the duo's synth-pop. “Alien” is a halting, bittersweet ode; “My Heart… So Blue” is a haunting, guilt-ridden farewell. The skeletal, sparkling “Siren Song” is an exquisitely detailed miniature meant to capture the immeasurable sweep of pain and joy.