As CBS 2's Jessica Schneider reported, 2 billion people are expected to watch the concert worldwide, while the lucky few thousand will actually be inside Madison Square Garden. And while the music is happening, dozens of celebrities will be taking phone calls from people pledging even more money for Sandy victims.
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The celebrities had been streaming into the stadium all day, gearing for what has been billed as the biggest musical event ever staged in New York City.
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In between the songs, comedians such as Adam Sandler will take the stage.
When asked if he was excited for the concert, Sandler said: "Very. It's going to be nice."
The show is sold out, with all proceeds going toward Sandy relief. Tickets cost $150 to $2,500.
It is scheduled to go on for at least 4 1/2 hours, and some of the musicians playing come from the very communities that were hit hardest.
Jon Bon Jovi is originally from Perth Amboy, N.J.
"I heard the devastation in my hometown, which is on the bay, and when you see National Guard on Ocean Avenue in Sea Bright, your jaw drops," he said.
Bon Jovi added: "This storm lasted a day but the effects of it will last a lifetime. In our time of need, people come together in a way that is unique to who and what we are and I love that."
Billy Joel grew up in Hicksville, Long Island.
"Even the landscape is different. People were stranded, people died. It's traumatic," Joel said. "I'm a Long Islander. I'm proud to be an Islander, and to see something like this happen is devastating," Joel said.
Bruce Springsteen was born in Long Branch, N.J.
"There was just complete, entire buildings washed away into the sea, and a level of destruction I haven't seen," he said.
Sir Paul McCartney, of course, is a native of Liverpool, England. But he felt a calling to do his part as he witnessed the horrors wrought by Sandy.
"The idea that it's still leaving people suffering on the streets, without homes, power, without shelter, I think that's when suddenly everyone realized," McCartney said.
He continued: "Sandy had done so much damage, and there had been so much suffering, and when I heard there was to be a concert, I wanted to be there. I wanted to try and do my bit."
Every penny donated will go to Sandy relief through the Robin Hood Foundation.
"For me as a New Yorker, to see us all coming together to want to help each other really showed me what a great country we are," said Alicia Keys.
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And those lucky enough to get tickets are thrilled at the celebrity-studded collaboration and at the fact that they themselves have a chance to help.
"I think it's wonderful that everything's being donated for Sandy, and that Ticketmaster waived their charges, and I think it's great that all the artists got together," said concertgoer Cherylyn Burns.
"It's a wonderful cause," said concertgoer Judy Capritti, "because we all grew up going to the Jersey Shore, so it means a lot to us."
And it's not just about the celebrities. About 100 Sandy victims and heroes will be inside Madison Square Garden, and will be featured on video montages.
Among the Sandy victims at the concert will be Marwah Fathy. Sandy flooded and destroyed her family's home on John Street in Old Bridge, N.J.
"We're still not allowed back to the house. They are saying that the foundation is not secure," Fathy told CBS 2's Emily Smith. "And, so I have kids, and so I'm not taking chances."
But Fathy is now feeling lucky, because she is going to the benefit concert as one of about 100 Sandy victims surprised with tickets.
Her ticket came from Verizon Wireless, her employer.
"They said, you know, 'Are you interested in going to a concert?' which at that time, I had no idea what concert it was, and how big it was, and how exciting," Fathy said. "Just knowing that it is for Hurricane Sandy victims, it just makes it that much more special to me."
The concert will be Fathy's first ever.
The concert will include performances by Bon Jovi, Eric Clapton, Dave Grohl, Billy Joel, Alicia Keys, Chris Martin, The Rolling Stones, Springsteen with the E Street Band, Eddie Vedder, Roger Waters, Kanye West, The Who and McCartney.
In one of the more interesting mixes onstage, McCartney will take the place of the late Kurt Cobain onstage in a reunion of Nirvana, along with Grohl and Krist Novoselic.
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