“Down,” the latest release from the duo of Marian Hill, begins with the graceful, jazz-oriented keys paving the way for Sam Gongol’s elegant vocals. As your swept into the seductive subtlety, the afterburners of a glitchy, electro-percussive beat kick in. That low, warming flame switches gears into a hyperactive call to action, before simmering down and then raising it up again. The heat rises, yet Gongol maintains her cool.