Livro captures Caetano Veloso at his sensitive best: His voice is the primary instrument here, as delicate and precise as a fingertip tracing a pattern on your skin. The heat lies, paradoxically, in his restraint: Brazil’s Carnival rhythms constantly shift and clap underneath songs like “Os Passistas” and “Onde o Rio e Mais Baiano,” but they never explode. Meanwhile, the celestial “Um Tom” feels like a mission statement, of sorts, for Veloso’s restlessly experimental career.