Stephen Wrabel is the rare songwriter whose own voice (literal and figurative) is so powerful that he often features on the songs he writes with pop stars like P!nk and superproducers like Afrojack. The Berklee music-school dropout excels at classic piano-crafted melodies that pull hard on heartstrings, but it’s the casual intimacy of his detailed lyrics that makes him an essential collaborator in an era of introspective yet empowering anthems.