Would the Woodstock Music and Arts Fair of August 1969 maintain its sturdy cultural significance without the 1970 film Woodstock, the Oscar-winning documentary that captured the event in all its muddy, drug-infused, glory? Probably. In the face of massive obstacles (traffic, sanitation, weather) this unprecedented gathering of 400,000-plus youths was both a stunning display of communal cooperation and the occasion for a score of legendary musical performances. Not something easily forgotten. Yet there’s no denying the enormous role that the film played in cementing the festival into our historical consciousness. This reissue marks the event’s 40th anniversary, offering a director’s-cut expansion and a third DVD with additional, previously unreleased numbers. Some of the added material reminds us how much deplorable music was endured by attendees: for all the stirring performances the official film captures — the Who, Richie Havens, Jimi Hendrix, among them — this version also serves up the grueling white-boy blues offerings of Canned Heat, the Paul Butterfield Blues Band, and the Grateful Dead. These are thankfully offset by new footage of Creedence Clearwater Revival’s compact, butt-kicking “Born on the Bayou” and “I Put a Spell on You.” DVD bonuses aside, Woodstock remains a marvel — one of the handful of music-related documentaries deserving of its continued reputation. To their vast credit, director Michael Wadleigh and his team of editors (chief among them a young Martin Scorsese), resist the temptation to concoct a self-congratulatory cinematic love fest of hippie unity. Rather, with their brilliantly realized use of split-screen action, the filmmakers present the festival in full: we hear from counterculture sloganeers, suburban kids out of their element, locals both exasperated and embracing of the unexpected invasion. And never is the accumulating filth much out of sight.