The answer to this is B. Pete Seeger. Aside from being an American folk singer, he was also known as a social activist. He used the radio to state his opinions and to help people become more informed about the things that they have to do.
He was a performer for more than 70 years and he has managed to make a lot of people happy and entertained. As an activist, he focused more on different environmental issues, civil rights, and also international disarmament. When he died of natural causes, people paid homage to whom they consider to be the pioneers of contemporary folk music.