Silvio Rodriguez's "Una Sombra" is a really interesting and almost mysterious song about a shadow that grows from something barely noticeable to something powerful. He sings about "una sombra imperceptible al mediodía" [a shadow imperceptible at midday], which makes you think of something tiny, almost invisible in the bright sun. But then this shadow, which "jamás lo parecía" [never seemed like it], starts to grow.
It's like this small, unassuming thing slowly becomes dominant. The most striking line is when he says, "es la sombra que hoy sorprendo devorando el amor" [it's the shadow I surprise today devouring love]. That's such a strong image! It suggests that this shadow, which started so small, has now consumed something as vital as love. The song ends with "una sola que no vive bien" [a single one that doesn't live well], leaving you with a feeling of something incomplete or troubled, perhaps because of this all-consuming shadow.