This fascinating documentary traces the roots of freestyling back to the rhythmic sermons of Baptist preachers, the improvisational energy of jazz music, and the spoken word artistry of the civil rights era’s Last Poets — but, like the form of rap it chronicles, it largely exists in the moment. The ephemeral nature of freestyling makes it a tricky thing to bottle, but The Art of Rhyme does so by mimicking the freewheeling energy of the MCs onscreen. And there are many legends of the medium featured here: from underground titans like Supernatural and Craig G (whose epic battles are shown here) to big names who crossed over into recording success like Talib Kweli, Mos Def, and even precious footage of a 17-year-old Notorious BIG. It’s as enlightening as you’d hope, but what makes this documentary such an impressive portrait of freestyle are all the ways it mirrors the impulsive, quick-thinking philosophy of the form in little over an hour.