There are a few elements that reliably form the basis for an Alicia Keys song: heartache or infatuation, an essential tenderness and emotion made heavy with wisdom, a patiently unfurling melody and, of course, that voice, yearning and ready to break, even as it remains in control. Even though these building blocks have helped her stand apart from pop trends while forging a remarkable career, Keys says the making of a classic song is still a mystery to her.