No one knows better than Yoko Ono how far celebrity activism has come in the last 40 years.

With late husband John Lennon she sparked a generation of celebrity cause campaigning with their 1969 Bed-In honeymoon to demonstrate for world peace as the Vietnam War raged.

From Live Aid, Band Aid and even Farm Aid in the 1980s to Bono's tour of Africa with U.S. Treasury Secretary Paul H. O'Neill earlier this decade, pop-star involvement in everything from politics to poverty reduction is ubiquitous.

But it wasn't always that way.

When John and I were sort of talking about world peace and love and all that kind of thing, bed-ins, etc, you know people were just laughing at us, Ono told Reuters.

But now I think that everybody is involved because we just know that we have to do something about this world.

Ono has now teamed up with Hard Rock International for an Imagine There's No Hunger campaign. Like her earlier initiatives, music is as central, including a song by Lennon, but its use has evolved to accommodate the online generation.

The campaign, which will raise money for non-profit anti-poverty group World Hunger Year, harkens back to Lennon's 1971 ballad Imagine.

To raise money for WHY the campaign is releasing an album, called SERV4, for download.

The album costs $12, with the songs selling for $0.99 each. It will be available through the Hard Rock cafes, hotels and website beginning November 9, with downloads also from iTunes and Amazon.

Rock group O.A.R. is donating a live track of their song Lay Down to the digital album, which will also include Lennon's Gimme Some Truth.

It will also feature versions of rare, live or previously unreleased tracks from Elvis Costello, Eric Hutchinson, Brett Dennen and others.

Ono says she finds hunger a particularly poignant issue due to her own childhood.

In the Second World War I was in Japan and as kids we were made to evacuate in the countryside ... and all the city kids were really starving, she said.

So I remember that feeling and it's just a very unpleasant feeling. It's just a very cruel thing to do to kids.

Whether the new generations of activist celebrities harken back to Lennon and Ono's legacy doesn't matter, she added.

They don't have to necessarily think that it was our legacy or something like that, Ono said.

Let them to do what they think that they can do and it's very important, instead of sort of towering over them and saying, 'We did it.'