During the summer of 1969, a Chicago studio group produced a single record called "Hey Hey! Holy Mackerel! (The Cubs Song)" whose title and lyrics incorporated the catch-phrases of the respective TV and radio announcers for the Cubs, Jack Brickhouse and Vince Lloyd. Several members of the Cubs recorded an album called Cub Power which contained a cover of the song. The song received a good deal of local airplay that summer, associating it very strongly with that bittersweet season. It was played much less frequently thereafter, although it remained an unofficial Cubs theme song for some years after.

What year was the single "Hey Hey! Holy Mackerel! (The Cubs Song)" produced?