Based on the critical reception to Chief Keef’s pair of self-released 2013 mixtapes—August’s Bang, Pt. 2 and October’s Almighty So—you’d think the rapper had fallen off as suddenly as he’d gotten on the year before. And to be sure, compared to the catchy, zeitgeist-capturing anthems of Finally Rich—Keef’s 2012 studio debut—Almighty So feels a bit obscure. The album sounds as though Sosa had officially chosen the road less traveled, burrowing deep into occasionally atonal beats and cloaking his bars in thick atmosphere. But the results of all of that experimentation are fascinating, and history has been kind to Almighty So, which might be Keef’s most influential release, one that finds him pioneering a slurry, intuitive style that sounds perfectly standard today. And a few tracks here are downright essential to his canon, like the riotous “Ape Shit,” which is punctuated by slasher-fic screams, and the perceptive “Self,” on which the rapper asks, “They want that old Sosa—for what, though?”