21 Savage, Migos' Offset, and Metro Boomin have all worked tirelessly, if only occasionally together, to become some of hip-hop’s most in-demand collaborators. Without Warning, an album whose release lives up to its name, is a return to the MCs’ trap-music roots (after having achieved a fair bit of pop appeal). The whole of it is dark and dense with highlights like the admonitory “My Choppa Hates N*ggas” and “Run Up the Racks,” a song whose muffled keyboard chimes cast an eerie pall over brags of ill-gotten income. The woozy Offset solo outing, “Ric Flair Drip,” is one of the few more jubilant moments.