Rugged Atlanta rap gets a new dynamic duo on a murky, minimal EP that brings out the best in its precocious players. For producer Metro Boomin—in-demand architect of Drake and Future’s irrepressible “Jumpman”—it’s a chance to darken his palette with foreboding bells (“No Heart”) and muffled 808s (“Feel It”). And then there’s 21 Savage: dabbling with playful, raspy boasts (“Mad High”) while never losing the hard-edged authenticity of a true trap king.