Pete Seeger, the singer, folk-song collector and songwriter who spearheaded an American folk revival and spent a long career championing folk music as both a vital heritage and a catalyst for social change, died Monday. He was 94 and lived in Beacon, N.Y. Mr. Seeger’s career carried him from singing at labor rallies to the Top 10 to college auditoriums to folk festivals, and from a conviction for contempt of Congress (after defying the House Un-American Activities Committee in the 1950s) to performing on the steps of the Lincoln Memorial at an inaugural concert for Barack Obama. In his hearty...