This week we're celebrating the 50th anniversary of hip-hop. We'll hear interviews with some of the most influential rappers and DJ's of the past few decades. Today, we kick things off with three hip-hop pioneers. First, DJ Kool Herc, who is considered the first DJ to isolate the breaks — the most danceable beats in a record — and repeat them to keep the dancers going.Then, Grandmaster Flash, who was one of the first DJ's to make successful recordings. He'll describe some of the turntable techniques he developed.Finally, we'll hear from Melle Mel, the rapper with Grandmaster Flash and the Furious Five. Their record "The Message" was the first successful rap record that offered social commentary.