Kesha crash-landed into pop with a toothbrush and a bottle of Jack. Her take-no-prisoners attitude echoes larger-than-life personas like electro provocateurs Peaches and M.I.A., and her hip-hop-tinged style recalls “Hollaback Girl”-era Gwen Stefani. But she's also taken guidance from songwriting legends like Dolly Parton and Elton John, whose craft and resilience inspire the country-rock aesthetic and inner strength that define 2017's Rainbow.