In the almost four years between PRISM and Witness, one of pop music’s most consistent hitmakers went through a period of emotional, physical and political transformation—she fell in and out of love multiple times, went on the 2016 campaign trial with Democratic nominee and presidential runner-up Hillary Clinton, and sported a head-turning platinum pixie cut as if shedding away a younger, more naive version of herself. She also entered her thirties. Does one major life milestone matter more than another in this case? Probably not, but it might help explain the contours of Katy Perry’s fourth, and most divisive, major-label album—a self-described “purposeful pop” project with sinister synthwave edges, centred on a pleading, forthright hope that society will become better. Perry’s music has always had a liberatory streak, but Witness is most on the nose with its political intonations. “Chained to the Rhythm” (featuring Skip Marley) enlists Perry’s longtime collaborator Max Martin, synth-pop star and friend Sia, and the grandson of “Concrete Jungle” singer Bob Marley himself to spread a cautioning message about the walls we build to hide governmental atrocities, all wrapped up in glistening euphoria. It gives the sense that Perry might be singing more for herself than anyone else—the artist felt her conservative Pentecostal past was retriggered by the shock of the Donald Trump presidency, and she felt empowered to act on her sadness not just personally but publicly. To that end are songs about obliterating self-made boundaries with no pretence: the Nicki Minaj-aided “Swish Swish” is a slamming diss track with a moody house beat, while “Bon Appétit” (featuring Migos) celebrates the fine art of dining on carnal pleasure with an addictive, tropical bounce, Perry sashaying through a charcuterie board of double entendres with her signature nonchalance. But it’s on Witness’ less avant-garde tracks that her political and melodic voices truly shine in tandem: the groovy retro-soul of “Pendulum” highlights her deep vocals powering an uplifting self-acceptance missive, and on the soft ballad “Into Me You See”, she sings the praises of a loved one who sees beyond her hardened public shell. For Katy Perry, even the most dramatic of changes can’t hide a person’s inner spirit.