Near the end of “B.O.R. (Birth of Rap),” the first song from his 2009 DIY triumph, 6 Kiss, Lil B sets the bar high for productivity: “You ain’t in the game until you make a thousand songs.” Born Brandon McCartney in Berkeley in 1989 and raised around the Bay Area, B was rapping by the time he entered high school. Aged just 15, he and three friends formed The Pack; in 2006, they scored an unlikely crossover hit with “Vans,” a spare, lighthearted ode to the affordable shoes. That song fit in with the minimal sounds that dominated rap in that era. But instead of chasing it into mainstream stardom, B disappeared, biding his time until he could reemerge with something that would turn the genre on its ear. Beginning with 6 Kiss, B liberated himself completely from rap’s conventions, free-associating, breaking rhyme patterns, defying the laws of physics, syntax, and decorum. His formal experiments poured out in never-ending deluges across his social media pages. Whole subgenres—based music, cloud rap—seemed to spawn from his rib, and continue to be perfected on the sprawling, delightfully formless albums that drop with little warning.