It was the most audacious sounding mash-up of megalegends, but just the kind of thing that would be a highlight of a show full of them, “12-12-12: The Concert for Sandy Relief.”

Paul McCartney fronting Nirvana, standing in the place where Kurt Cobain once stood.

In the middle of what otherwise was a regular set by Sir Paul and his band, divided between Beatles and Wings songs (and one solo ballad, performed with Diana Krall), the first reunion of Dave Grohl, Krist Novocelic and Pat Smear came with the ex-Beatle at the front, jamming on a song they had practiced called “Cut me Some Slack,: with lyrics that sounded lifted from Mary Robbins’ “Devil Woman,” a sound echoing Led Zeppelin, and a hard-hitting presentation that seemed an echo of his own “Helter Skelter,” with which he began his set.

It was one of a few interesting collaborations in the long show from Madison Square Garden, carried on dozens of networks, and sent out to a potential audience of 2 billion. Just before McCartney’s late set, which began at 12:30 a.m. and didn’t end until after 1, Chris Martin of Coldplay performed solo, until he brought out a grey-bearded Michael Stipe out of retirement and they traded verses on his old R.E.M. hit “Losing My Religion.”

Jon Bon Jovi seemed pleased to be brought out to help sing “Born to Run” to close out the opening set by Bruce Springsteen & the E Street Band, a strong set that began with “Land of Hopes and Dreams” and included “Wrecking Ball” and “My City of Ruin,” in a version that worked in both “Working on a Building” and “Jersey Girl.” But then Springsteen had to come out during Bon Jovi’s set to help sing “Who Says You Can’t Go Home.”

Roger Waters brought in Eddie Vedder during his set of songs from “The Wall” and “Dark Side of the Moon” — and he also had a troupe of dancers.

It was largely a night of classic rock by bands who survived for decades, from the Rolling Stones, who presented a short two-song set, and The Who, whose set was much longer. A further giant of 60s rock, Eric Clapton, also played.

“It’s weird to be the youngest member on a bill like this,” Martin, the 35-year-old Coldplay singer  told the crowd. “If you’re going to donate tonight, just think of a figure which you might think might be the average age of of the performers. I think we’ll raise billions.”

Money totals collected by celebrity phone operators were never given, though they kept saying it would be “record breaking.”

None sang songs that were directly about the storm, save for Billy Joel’s prescient “Miami 2017 (We Saw the Lights Go Out on Broadway),” part of a strong and well-received set by the Long Island native.

Just about the only acts representing a younger fan base were Kanye West, who appeared to wear a skirt and did just about every single he ever recorded, and Alicia Keys, who in addition to her own emotional set, returned at about 1:30 a.m., after McCartney’s final song, “Live and Let Die” to cap the night with her modern day anthem for the city “Empire State of Mind.”