Deep Purple – Child in Time
Someone told me that "Deep Purple in Rock" is the best prog. rock album in the world. I'm not the biggest prog. rock fan, however, "Child in Time" might be the best prog. rock song. If you've never heard it, you're in for a real treat.
PS - Rock n' Roll Hall of Fame, listen to this, and listen to Grand Master Flash and tell me who should be in your crummy hall.