Like all the best artworks, it's about something very basic (the brewing of beer), at the same time something deep & esoteric (death & renewal). Local and historical-specific traditions get grafted on, much like the Dionysus myths of classical & pre-classical Greece, where specific tensions are played out, such as political & religious power changes (cf. later Temperance Society type interpretations). That's what I think anyway, for what it's worth - enjoy the song & find your own special meanings!