Britain’s Union Square Music specializes in low-priced compilations that dip, usually impressively, into virtually every genre extant. The label’s “Simply” series, having previously offered samplings of everything from blues to reggae, smooth jazz to Latin, now presents this more ambitious four-disc, no-frills overview of the sounds of, well, some parts of the world. Heavily weighted toward Latin, Brazilian, African and Asian tracks licensed from a variety of sources, Simply World hops around merrily and seemingly randomly: the first two discs alone name-check Gilberto Gil, Celia Cruz, Khaled and Oliver Mtukudzi. Such a hodgepodge could, in lesser hands, result in a jarring sonic clash, but these four distinct programs—divvied thematically into discs sub-headed “World Party,” “African Moves,” “Acoustic Adventure” and “Nu World”—each flow effortlessly, kiboshing those notions of indiscriminate programming. Despite a dearth of marquee artists, ultimately it’s the third and fourth discs that offer the most thrilling surprises, each veering closer to an opposite edge of what constitutes contemporary world music. Calling this box essential, as the liner-note-less set’s title does, might be something of a marketing stretch, but calling it revealing isn’t.