Pete Seeger is entertaining and leading a crowd in a sing along. Among is causes was the environment and this annual festival was instrumental in calling attention to and cleaning up the pollution in New York's Hudson River. This is from 2007 and his voice was considerably weakened so almost all the songs had audience participation; he loved to get a crowd singing.
The Clearwater Festival (officially The Great Hudson River Revival) is a music and environmental summer festival and America’s oldest and largest annual festival of its kind. This unique event has hosted over 15,000 people on a weekend in June for more than three decades. All proceeds benefit Hudson River Sloop Clearwater, Inc., a nonprofit 501(c)(3) environmental organization. The Festival was founded in 1966 by Toshi Seeger and her husband, folk singer Pete Seeger, who regularly performs at it. (Wikipedia)