Ani DiFranco's latest disc, Canon (the singer/songwriter's first retrospective recording), showcases the new mother's contribution to music — an influential career that's spawned 19 albums. DiFranco has admitted to the headache involved with compiling a best-of collection: the disc spans nearly 20 years of her signature political folk rock, including a few early fan favorites she probably didn't want to revisit. Regardless, Canon is DiFranco's definitive record, traveling from fiery youth to focused reflection. Tonight, her legions of fans flock to glimpse the singer's famously passionate live show.