Forty years ago, Chuck D showed listeners how exciting, radical, and unpredictable hip-hop could be. His song “Fight the Power” became a protest anthem for a generation, and a Greek chorus in Spike Lee’s film “Do the Right Thing.” The Public Enemy front man talks with the staff writer Kelefa Sanneh about his life in music. “I wanted to curate, present, navigate, teach, and lead the hip-hop art, making it something that people would revere,” he says. Now, at sixty-two, Chuck D is an elder statesman of his genre, and also a critic of it and some of its more commercial impulses. His latest project is a four-part documentary, “Fight the Power: How Hip-Hop Changed the World,” which is airing now on PBS. “I’ve been to one hundred sixteen countries over thirty-eight years, so I’ve seen the changes,” he says. “People have made their way to me to say, ‘Chuck, this is what this art form has meant to me,’ in all continents except for Antarctica.”