Martin Scorsese's sprawling meditation on the rise of street gangs in 19th-century New York (the roots of the modern mafia) also became another soundtrack buff's "What If?" after the director scrapped the original orchestral underscore of modern collaborator (Cape Fear, The Age of Innocence, Bringing Out the Dead)/veteran scoring legend Elmer Bernstein and replaced it with this typically rich, Robbie Robertson-supervised collection of eclectic pop, folk, and neo-classical tracks. The latter come courtesy of three brooding excerpts from film composer Howard Shore's previously unpremiered concert piece Brooklyn Heights, tracks that help emphasize the film's darker emotional gravitas. Much of the other catalog choices by Robertson and Scorsese lean on an evocative slate of Celtic and folk-tinged selections that range from hammered dulcimers, fiddles, and tin whistles to the spare, emotive balladry of Linda Thompson and Shu-De; even U2's main theme, "The Hands That Built America," is cast in a similar mold. But that Irish musical stew gets leavened by everything from the postmodern dirges of Peter Gabriel and Jocelyn Pook to a black field hand recording by legendary musicologist Alan Lomax and even the Chinese flavors of "Beijing Opera Suite." It's an imaginative, compelling mix, one that gratifyingly pushes the usually staid boundaries of what film scores can truly encompass.