We may look back on the mid-to-late 10s as rap’s Silver Age, a time when listeners rewarded experimentation, and artists pushed the limits of semi-melodic flows and intricate beats. “Sicko Mode” gives hip-hop its own “Paranoid Android,” a numbed-out rug-pulling epic. Valee and Sheck Wes push rap into haunted house minimalism, complete with zombified sing-song verses. Then there’s “XO Tour Llif3,” the accidental smash that veers between sounding like Post Malone and Future at his most anguished, a snapshot of a man on the edge.