Etched with Argentine folklore and fueled by the rap batallas of Buenos Aires, Milo J’s songs call upon the cumulative spirit of the centuries. “Sometimes words come to me that I haven’t heard before,” he told me afterward, as if to summon a life he’s never lived. In arenas and stadiums, the 19-year-old connects with his young peers about the passage of time with great energy and intensity. At the Tiny Desk, he takes a beat: Stripped back, yet deeply fortified, Milo J emerges with a new softness and depth.