Like a candy apple with a razor blade hidden inside, Red Velvet's songs have a sugary appeal that conceals a sharp-witted core. The versatile girl group has two faces: First, there's the “Red” side, which gleefully smashes together electronic, synth-pop, funk, and hip-hop to create upbeat, unpredictable pop rockets like 2015's “Ice Cream Cake.” Then there's their softer “Velvet” side, where they lend their pretty voices to wistful ballads and silk-smooth R&B (like their note-perfect cover of S.E.S.'s “Be Natural”).