In many music documentaries, live performances grind the narrative to a halt, and as good as the performances may be, they leave viewers with the suspicion that they’re why the movie exists - to show them, and that the whole project is an extended, very public act of fandom. When Lily Keber’s Bayou Maharajah: The Tragic Genius of James Booker screened at this year’s New Orleans Film Festival, the vibe was far less indulgent. Sequences of Booker in concert were more than See? Look! Wasn’t he great?! moments.