Miley Cyrus puts in overtime to be the most unpredictable star of her generation, and pop is all the better for it. The singer has poured the ups, downs and utter weirdness of growing up famous into a string of post-everything gems, each one subversively unique. Heartland ballads as wholesome as apple pie sit precariously alongside hip-hop bangers rife with provocative talk. One minute her voice bops and bubbles to glittery electro-pop, the next it's boasting and taunting over caffeine-fuelled punk riffs. The sound of confounded expectations has never been filled with more pop hooks.