The “Various Artists” rack of the hip-hop section at your local record store will yield countless “old school” sets–some solid, some weak. But this two-disc collection, compiled by music historian Ian Dewhirst, is one of the more enjoyable ones around. Disc One deftly documents the early ’80s–a time when hip-hop could be socially alert yet very danceable (“The Message,” “It’s Like That”) and was tailored much more to b-boys (“Break Dance”). Disc Two, covering the mid-’80s to early ’90s, isn’t quite as fun, and seems scattered (where are Public Enemy and Eric B. & Rakim?), but Dewhirst at least includes golden-era bangers from The 45 King and Jungle Brothers.