Let’s try to keep calm, because, for all of its ambition and grandeur, this new Rosalía album, “Lux,” demands a sharpened mind more than a blown one. It’s an opaquely themed, scrupulously produced concept record in which the Spanish pop auteur sings about a handful of saints and martyrs in more than a dozen languages, backed by the unmitigated power of the London Symphony Orchestra — a stacking of lavish gestures that Rosalía hopes might help elongate our diminished online attention spans.
