Encapsulating the history of R&B in a box set, even one that spans six discs, is a ridiculous task. Inevitably, there will be important artists and songs that are missing, no matter how comprehensive the set is. Rhino's R&B Box -- 30 Years of Rhythm and Blues suffers from that very problem. While it contains some of the classic tracks, it lacks contributions from giants like Sam Cooke, Hank Ballard, the "5" Royales, Stevie Wonder, and Sly Stone, among others. What is left is more or less excellent -- it's hard to argue with a set that includes "The Girl Can't Help It," "Young Blood," "Reet Petite," "Maybe," "For Your Precious Love," "Kansas City," "I Only Have Eyes for You," "Gee Whiz," "At Last," "Spanish Harlem," and "Blue Moon" on one disc, after all. Since it features so many hits, the set sounds like an oldies radio station, stringing one classic after another. That alone makes it a worthwhile experience. It's just not a definitive compilation.