In 1973, in the rec room of a Bronx apartment building, Clive Campbell—stage name: DJ Kool Herc—and his sister, Cindy, put on a “Back to School Jam” party. Hip-hop was invented then and there, at 1520 Sedgwick Avenue. That year, every crumbling street corner in the Bronx sprang alive with “Masters of Ceremony” (or “M.C.s,” as they became known) and nascent D.J.s, who remixed dated disco records. In 1979, “Rapper’s Delight,” by the Sugarhill Gang, hit the Billboard Hot 100 chart. Over the next 10 years, the obscure musical genre began its climb into the mainstream. This show, co-curated by Sally German and Sacha Jenkins, presents portraits of pioneers Nas, Tupac, Mary J. Blige, and Notorious B.I.G., as well as images of hip-hop’s current stars. —Elena Clavarino