Twenty years ago this month, the number one single in Britain was the benefit song “Do They Know It’s Christmas” performed by an all-star cast of British musicians – including Sting, Boy George, George Michael, Phil Collins, and Bono – calling themselves Band Aid. This year, a new version of the same song, featuring an updated cast of Thom Yorke, Robbie Wiliams, Chris Martin, Bono, and Dizzee Rascal, is once again atop the British charts.

It hasn’t received much attention stateside, where it’s only available as an import. And for the younger generations who hear it, it may not make much of an impression. (The only distinguishable voices are Bono, who sings the same line he did on the original, and Dizzee Rascal, who performs a mostly unintelligible rhyme.) But for those old enough to remember, it recalls a uniquely purposeful moment in pop history.

The year 1985 was one of excess and frivolity, in society and music. It was pop at its poppiest – its most saccharine and superficial. Yet, somehow, it was also a time of unprecedented – and as yet unequaled – charity and social consciousness, for it was the year of Live Aid, the African famine relief effort (organized by the Band Aid Charitable Trust). Live Aid culminated, on July 13, in simultaneous concerts at Wembley Stadium, London and J.F.K. Stadium, Philadelphia.

A new four-disc Live Aid DVD set celebrates both the music and the spirit that made this event possible. It is a concert film of the largest concert – and arguably the single most unifying event – in music history. For years, the concert footage was prevented from being rebroadcast because organizers believed Live Aid would be more powerful in memory than in reality. But memories fade, and the new DVD is a welcome reminder of the music community’s one-time potency and unity of voice.

Live Aid involved too many stars to list: Bob Dylan, David Bowie, Madonna, Paul McCartney, Sting, Queen, U2, Mick Jagger, and the Who just scratch the surface. (Ironically, it opened with a band called Status Quo). It was simulcast to an estimated audience of 1.5 billion people around the world and raised $80 million for African famine relief in 1985 alone. In the 20 years between the release of the first Band Aid single and the Live Aid DVD, the Band Aid Charitable Trust has contributed $144 million to relief and development efforts on the continent.

But even these numbers, impressive as they are, don’t capture the full impact of the effort. The Band Aid single and Live Aid concert had an incredible galvanizing effect, making African famine relief a worldwide cause celebre. They motivated governments – most notably Britain and the United States – to step up aid to Africa, and spawned similar efforts around the world. Twenty famine relief records were released in 1985 alone, including the hugely successful USA for Africa single “We Are the World” (written by Michael Jackson and Lionel Richie and produced by Quincy Jones,) which contributed more than $62 million to the cause. (At Jones’ request, Jermaine Dupri is organizing a 20th anniversary update, titled “We Are the Future,” to be recorded in February.). They also inspired like-minded movements such as Farm Aid, which was founded by Willie Nelson, John Mellencamp, and Neil Young in 1985 to support family-owned farms in America.

It’s likely none of it would have happened if it weren’t for Bob Geldof of the Boomtown Rats, who was inspired to organize the effort after seeing a BBC broadcast about the famine ravaging Ethiopia and sub-Saharan Africa (it’s included in the DVD set). But as impressive as the organizational feat of the concert, Geldof and his colleagues did their real heavy lifting behind the scenes in actually delivering the aid to the needy – a Herculean task in its own right, documented at the end of disc four.

The Band Aid Trust spent no money on administration. Volunteers worked from a disused bus terminal in London so that all the money they raised would be spent directly on relief. But the shoe string operation moved a mountain. Finding it was cheaper than commercial transportation, Band Aid chartered three ships of its own, which sailed to Ethiopia each week carrying medicine, tents, trucks, vegetable oil, grain, and flour – their own supplies as well as cargo that other charity groups couldn’t afford to ship. When famine developed in remote areas of neighboring Sudan, Band Aid bought a local trucking company to enable them to deliver supplies.

The Live Aid DVD, however, is useful as more than just a political reminder. It is also a time capsule, an indispensable document of mid-1980s music and culture. During her (unaired) performance, Joan Baez says to the Philadelphia crowd, “This is your Woodstock and it’s long overdue.” She’s right – but it’s a different kind of generational statement, one that has little to do with politics.

The mid-1980s was not a time of outspoken advocacy in music, and few of the songs performed during Live Aid were topical. Many, however, were performed as if they were. U2’s “Sunday Bloody Sunday” proves adaptable to any cause or situation, and Tom Petty’s “Refugee” takes on humanitarian overtones despite being about a damaged lover (“don’t have to live like a refugee”). But it’s Geldof and the Boomtown Rats who achieve the most poignant moment when they stop, fists in air, at the line,” And the lesson today is how to die!” from the song “I Don’t Like Mondays.”

These are the exceptions. For the most part, the entertainments here are openly light, frothy, and frivolous – in keeping with the spirit of the time. We see forgotten Day-Glo acts like Spandau Ballet performing their only hits, and emerging superstars like Madonna choosing between theirs.

But there are plenty of worthwhile moments for pop music buffs. Sting plays a nice, stripped-down version of “Roxanne,” backed by Branford Marsalis on sax. A mustachioed Freddie Mercury leads Queen in a show stopping six-song set that has the 70,000 fans singing along to “We Will Rock You” and “We Are the Champions.” And Phil Collins performs his piano ballad “Against All Odds” in Wembley, then, after a quick trip on the Concorde, does “In the Air Tonight” in Philadelphia. It reminds you just what a huge star he was.

The DVD also serves as an entertaining reference guide to mid-1980s style (and lack thereof). Bono wears leather pants and high-heel boots. David Bowie is dashing in baby blue and shoulder pads. Elton John looks like a disco babushka alongside a biker-leather-and-blue-jeans-clad George Michael as they perform “Don’t Let the Sun Go Down on Me.” And Kevin Cronin of REO Speedwagon wears what looks like a Technicolor housecoat and lady gym teacher hair.

Whether high-minded or low, the DVD is worthwhile for the nostalgia trip alone. But even more so than the music and fashion, you may find yourself wishing to revisit the sense of purpose and the moral clarity Live Aid represented.