Fifty years ago, a DJ spun some records in an unconventional way at a back-to-school party and created an art form that dominates pop music today. Hasan Jeffries is associate professor of history at The Ohio State University, and he joins host Krys Boyd to discuss hip-hop’s birth in the Bronx and its dual identities of both protest music and party music. Hasan was a consultant for and is featured in the documentary series “Fight the Power: How Hip Hop Changed the World,” which airs this month on PBS.