How did the Depression-era folk-song collector Alan Lomax end up with a songwriting credit on Jay-Z's song "Takeover"? Why doesn't Clyde Stubblefield, the primary drummer on James Brown recordings from the late 1960s such as "Funky Drummer" and "Cold Sweat," get paid for other musicians' frequent use of the beats he performed on those songs? The music industry's approach to digital sampling-the act of incorporating snippets of existing recordings...