Ariana Grande and Barbra Streisand impress Michael Buble equally

It was a totally organic moment that became a memorable one.

Michael Buble and his band were warming up in a hallway backstage during taping of his 2013 NBC Christmas special in his hometown of Vancouver when a producer overheard it, loved it and told him it should be in the show. The impromptu rendition of "Blue Christmas" became an incredibly strong opening number.

"It's funny, isn't it?" says Buble, who will host his fourth Christmas special when "Michael Buble's Christmas in New York" airs Wednesday (Dec. 17), on NBC. "Sometimes you have all these great techniques in miking and sound engineering and all of this, and then you just sit onstage with a bunch of guys and you hold a microphone over everybody and just let them go. Sometimes the simple things work best."

In fact, it worked so well that Buble is making it a more prominent part of this year's show, an unplugged section in which the Canadian crooner and his band will perform requests from his social media followers. As for the rest of the show, the hour-long special, which was taped at the iconic Radio City Music Hall in October, features the multiple Grammy Award winner welcoming guests Barbra Streisand, Ariana Grande, Miss Piggy and the Rockettes, with song selections including such holiday classics as "It's Beginning to Look a Lot Like Christmas," "Christmas (Baby Please Come Home)" and "All I Want for Christmas Is You."

For Buble, getting Streisand -- a Grammy, Oscar, Tony, Emmy and Golden Globe Award-winner -- was a major coup.

"You can imagine ... the high-fiving that went on in my office," Buble tells Zap2it. "I think she told me that it was 53 years or something that she's never done anything like this, and it meant a lot to me. ... It meant that she liked me as much as I like her, and I just have so much respect for her. She is someone who has never compromised the integrity of her art, ever -- ever -- and including this special. And she doesn't do it in a heavy-handed, mean way. She's just very honest and very real."

Buble was also impressed by Grande, the 21-year-old actress and singer best known for her role in Nickelodeon's "Sam & Cat" and her top 10 single "The Way." Her vocal range has been compared to that of Mariah Carey.

"Ariana Grande ... walked in and blew everyone away," Buble says. "Number one, her voice. I didn't know. I don't know any more when I listen to music who's for real and who's not. There's so much great work done with production that they can turn pretty much anybody into a singer. So when she walked up on stage -- I can speak for the boys in my band -- we were all blown away. Up walks this girl, this tiny, little thing, and she just killed us, she was so good."

Source: http://www.zap2it.com/blogs/michael_buble_christimas_in_new_york_ariana_grande_barbra_streisand-2014-12