'This Is Acting' is the seventh studio album by Australian singer-songwriter Sia. Sia's songs update the grandiose Eighties lite-rock ballad tradition of Diane Warren and Phil Collins for our moodier era of R&B-inscribed feminism, delivering lyrics about strain, perseverance and redemption over tracks that build from tensely foreboding verse to a titanic cathartic chorus. She's mastered the formula so well that she's made her seventh solo album a commentary on how hit songs are made. The tunes here were originally intended for - and then rejected by - major singers. It's a fascinating study in what it's like to live life imagining yourself in someone else's artistic shoes. 'This Is Acting' opens with two songs that Sia hoped to land on Adele's 25. Her approximation of the phrasing and tone of the world's most beloved singer over the roiling piano on 'Bird Set Free' is uncanny, while 'Alive' is a throwback soul crusher that would've been the hardest-hitting thing on that blockbuster LP. Other highlights, such as the industrial-strength anthem 'Unstoppable,' feel like they could've been recorded by a half-dozen artists, from Katy Perry to Miley Cyrus.