Angie Martinez takes a look at the impact of five decades of genre defining music in "Soul of a Nation" special, “Hip-Hop @ 50: Rhythms, Rhymes & Reflections." WATCH NIGHTLINE EPISODES: ABC: abc.go.com/shows/nightline HULU: hulu.tv/2wSmSrZ & WATCH THE FULL EPISODE OF HIP-HOP AT 50: RHYTHMS, RHYMES & REFLECTIONS -- A SOUL OF A NATION PRESENTATION: ABC: bitly.ws/IYJJ HULU: rb.gy/d5h5g #nightline #soulofanation #angiemartinez #hiphop #hiphopmusic #abcnews