Singer John Sebastian, founder of The Lovin’ Spoonful, made an impromptu appearance at the Woodstock festival.

Singer John Sebastian, founder of The Lovin' Spoonful, made an impromptu appearance at the Woodstock festival.

Singer John Sebastian, founder of The Lovin’ Spoonful, made an impromptu appearance at the Woodstock festival.

Singer John Sebastian, founder of The Lovin’ Spoonful, made an impromptu appearance at the Woodstock festival.