Even before Evan Mast cofounded pioneering indie-dance duo Ratatat in 2001, he made left-field hip-hop beats as E.Vax. Today, his rap productions remain faithful to Ratatat’s lean sound. On Kanye West’s “Jail,” he strips down to just vocals and overdriven guitar. On Nas’ “Adam and Eve,” he evokes New York hip-hop’s ’90s glory days. And on Kid Cudi’s “Pursuit of Happiness (Nightmare),” he channels classic boom bap through sing-song indie hooks.