Forty years ago, it seemed for one brief moment as though a disastrous, mud-soaked music festival that attracted so many people it had a larger population than all but one city in the state could be the beginning of a new world of peace and cooperation. That dream was quickly battered but still lives on in the magic that its name and its songs still evoke: Woodstock. This week, a new movie from Ang Lee covers the impact of the festival on the community that was its not-entirely-welcoming host. But the truly indispensible memento of the three days of peace and music is the award-winning original documentary from director Michael Wadleigh. A new 40th-anniversary edition is being released this week with additional footage from from Paul Butterfield, Creedence Clearwater Revival, The Grateful Dead, Johnny Winter & Mountain and interviews from participants including Wadleigh and concert producer Michael Lang. Whether you remember the warning about the brown acid and the interview with the porta-john guy and the nun flashing the peace sign or whether you have yet to experience the “Fixin’ to Die” rag or Hendrix’s stunning “Star Spangled Banner,” this is a brilliant film about an extraordinary moment.