The men of the musical group Staff Benda Bilili are extraordinary in more ways than one: They live on the chaotic streets of broken, hard-luck Kinshasa, in the Democratic Republic of Congo; four of the singer-guitarists are paraplegic, disabled by polio; and their music is infectiously exuberant. Shot over a period of years (during which we watch their newest member, a self-taught musical prodigy, grow into a man), this unsentimental, smartly assembled film is equally attentive to the cacophony of African poverty and the balm of harmony provided by these pied pipers of hope. A-