Christmas is a time for family togetherness. No one need tell the Wainwrights that. To that end, the whole clan will host a family gathering at Carnegie Hall on Wednesday night, with guests like Lou Reed, Laurie Anderson, and Emmylou Harris.

Rufus Wainwright and sister Martha say the seeds of this tradition can be traced back to their mother, folk singer Kate McGarrigle. "This is really my mother's baby," Rufus tells Spinner. "It's Kate McGarrigle's dream that we're all reenacting here and she definitely made it mandatory to sing during the holidays up in Quebec, Canada, in order to basically show off how talented we were."

While the Wainwright brother and sisters joke around a lot doing a rare interview together, there is a serious note to the show, as it will benefit cancer research, an issue that is very personal to them. "[Kate's] been battling cancer for the last three years and part of the show is also a cancer benefit for the McGill University Cancer Hospital," Rufus explains. "And there are also some high-priced tickets left for the charity, which come with a bunch of perks."

"One of the great unsung perks is Kate has been baking these f---ing cookies," Martha says, laughing at the goods each luxury ticket holder will receive.

But, let's face it, the guests don't hurt, either. "If you put on another pair of glasses, you can actually picture them as archetypal Christmas characters. Is there anyone more elfish than Laurie, or like a little Christmas sprite?" Rufus says. "And what about Lou as a Scrooge or the Grinch? And it's great to have Jimmy Fallon as the alcoholic uncle."

As for the show itself, the Wainwrights have a few treats planned. "I'm gonna try and take a tab at 'Christmas Wrapping,' sung by the Waitresses, which is really tough," Martha says. "Hopefully we'll blow the roof off Carnegie Hall and they won't charge us for it. And I was also just running through 'Silent Night' in German with my boyfriend, who's German, and we're sounding very frightening."

"Frighteningly good," Rufus chimes. "Frighteningly beautiful."