Madrugada refers to the very early hours of the morning, typically from midnight until dawn. It's a more specific and evocative term than just saying "morning."
In "No Digas Nada," the word sets a clandestine and romantic mood. The lyrics "Esperemos juntos la madrugada" (Let's wait together for the early morning) and "Tres de la mañana y solo yo quiero ver / Cómo tu vestido se comienza a caer" (Three in the morning and I just want to see / How your dress begins to fall) highlight a secret, late-night encounter that extends into the quiet, intimate hours before the sun rises, emphasizing the secretive nature of their rendezvous.
Mario Bautista's "No Digas Nada" is all about a secret, late-night rendezvous. The singer knows the person he's singing to wants to see him, even though she's with someone else. He's confident she'll "apagarás el cel y conmigo verás el amanecer" [turn off your phone and with me you'll see the sunrise].
It's a pretty bold song, with Mario describing how they'll end up together in his room, waiting for dawn, and making sure "Que tu novio de esto no sepa nada" [That your boyfriend knows nothing about this]. He even sings, "Solo te estoy dando más felicidad" [I'm only giving you more happiness], suggesting he believes he's what she truly wants. It's a fun, slightly scandalous peek into a secret romance!