For many pop stars facing down their second album, “maturity” means dour confessionals, but Charlie Puth flips the script, bringing grown-up emotion to these easy-to-love grooves. On first listen to the nakedly romantic lyrics and bump-and-grind beats of Voicenotes, it may be hard to imagine that this is the same guy behind the peppy acoustic ballads and big-budget pop that filled his 2016 debut, Nine Track Mind. “Attention” is the steamy, bass-up-front strut designed to flip Puth’s public persona from grinning nice guy to wounded R&B player, and “Done for Me” seals the deal with its electro-funk duet with Kehlani. But it’s the album’s deeper cuts that really reveal Puth’s uncanny feel for classic soul music, including the harmony-rich Boyz II Men collab “If You Leave Me Now” and the throwback-disco rush of the Hall and Oates cowrite “Slow It Down”.