After a busy 2015 that included albums (Barter 6), mixtapes (Slime Season 2), a slew of memorable guest spots, and a highly entertaining Instagram feed, the colorful and casually radical Atlanta rapper returns with I’m Up. Opening with a tribute to embattled underground hero Boosie (“F Cancer”), the mixtape showcases Thug’s ever-evolving eclecticism, sliding between hard-bitten street rap (“Hercules,” “Bread Winners”) and strange, atmospheric funk (“For My People”) without a flinch. As always, the anchor is Thug’s choppy cadence and soulful, seductive squawk—a stamp of authenticity that nobody else seems able to replicate.