Musical siblings Rufus and Martha Wainwright turned Carnegie Hall into their own private living room last night, offering fans a casually delightful way to celebrate the holidays with their extended family and closest friends.

It doesn’t hurt that the Wainwrights count Lou Reed, Laurie Anderson and Antony (of Antony and the Johnsons) among their dearest pals.

The two-and-a-half hour show began with a rousing group number, “God Rest Ye Merry Gentlemen,” in which the cast of a dozen — give or take — swapped heavenly harmonies and instruments with insouciant, familial flair.

With Rufus and Martha as convivial hosts — playfully tossing lyrics sheets at each other and battling for the spotlight — the evening zipped right along. The performers alternated between acoustic instruments, backed by a small but sturdy group that included piano and upright bass (no drums). The arrangements put the emphasis squarely where it belonged: on the rich harmonizing.

While this was clearly a secular affair, Rufus joshed early on that, “Jesus is in the house tonight, I tell ya!” Ever egalitarian, he later offered a song for those who celebrate Hanukkah, though it wasn’t a traditional Hanukkah tune. “There are no good Hanukkah songs,” Wainwright said, “so what we decided to do is sing a Hebrew song,” before launching into a soaring rendition of the folk song “Hine Ma Tov.”

Other show highlights: Laurie Anderson’s plaintive run through “Oh, Come, All Ye Faithful,” actor Joseph Gordon-Levitt’s passionate, self-penned anti-war song (accompanied by ukulele), and Rufus’s hammy “What Are You Doing New Year’s Eve.”

Former SNL star Jimmy Fallon injected some comedy into the already informal pageant, first with a strummy ditty about Christmas and then with a cheerful song and (tap)dance with Martha.

After a short intermission, a black clad Antony delivered a skeletal, chilling doo-wop version of the Elvis classic “Blue Christmas,” complete with his rippling vibrotto. And Martha, in robust voice, traded verses with her cousin Lily Lanken on the feisty shanty, “Rebel Jesus”

But as the adage goes, the crew saved the best — and most emotional — for last. Lou Reed brought down the house with his trademark snarl, transforming two Christmas classics, “White Christmas” and “Silent Night,” into his own minimal gems.

While an undisclosed illness forced matriarch — and concert organizer — Kate McGarrigle — to call off her participation in this year’s shebang (and a planned tour), she surprised the audience, performing with the ensemble in the final numbers. A seated McGarrigle played banjo and tenderly thanked the crowd for coming. Her presence registered emotionally (Rufus visibly welled up) and left the audience with the definite message that, for the Wainwright clan, it’s a love of music -– and each other — that keeps the family running.

[photo: http://tinybanquet.blogspot.com/]