The music producer Dr. Luke—pictured above second from right—has been the engine behind inescapable hits from artists like Katy Perry, Britney Spears and Miley Cyrus, but he never worked more closely with an artist than he did with pop star Kesha, eight of whose nine singles he wrote and co-produced. But rather than a close artistic partnership, Kesha alleges in a new lawsuit, their relationship was dangerous and predatory.