Jessica Vosk admits she's not religious. But that didn't stop her from adding the somber holiday song "Mary, Did You Know?" into her Christmas-themed album Sleigh. "That melody is really great … and it says, 'Mary, did you know?' over and over again. So I feel like Mary, just, didn't know, you know? Like, she didn't know," says Vosk. To celebrate the joy of the holidays, and her upcoming Carnegie Hall concert, see Vosk sing the classic in the video above, exclusively for Playbill.

Though Vosk is generally an upbeat person, she does appreciate the beauty of a sad Christmas song. That's why, in addition to upbeat songs like "All I Want for Christmas Is You," Sleigh has its share of more downbeat selections, such as "Winter Song" (a duet with Ariana DeBose). "I love a sad Christmas," says Vosk with a smile. "We could be a little depressica...I feel like the holidays can be very difficult for so many people because of loss or just melancholy memories, on top of it being a beautiful time. So I think it's okay to feel both of those things."

Vosk will perform at Carnegie Hall December 20 and 21, in an evening that will feature the New York Pops, as well as songs from Sleigh (yes, it's a pun) and other holiday favorites, both traditional and contemporary. And, Vosk teases, there will be special guests. She won't reveal who they are except one. "The guest I can talk about is Santa. And then, after the performance, I can say the famous line in Elf, 'Santa, I know him!' And that will be a Jessica Vosk line now, in addition to Grey Henson," she says, with a manicured hand raised for emphasis, "who I love and adore, and I saw him at the opening of the fantastic Elf [on Broadway]." 

Besides preparing for Carnegie Hall, Vosk is also rehearsing for Hell's Kitchen. Beginning December 12, she takes over for her friend Shoshana Bean in the role of Jersey, the mother to piano prodigy Ali, in the Alicia Keys jukebox musical. For those used to Vosk's classic musical theatre belt (in such roles as Elphaba in Wicked), you might be surprised to hear her take a funkier tone in Hell's Kitchen. And yes, it's been intimidating to sing in front of Keys, but she's also grateful.

"I'm excited and scared. There's soul. There's a lot more soul in there. There's a lot more grit. So it's daunting, but I wanted a challenge, and I asked the universe for a challenge, and boy, did they deliver!" she exclaims with a nervous laugh. "Coming into it, of course, my take is very different, and I have been able to watch Shoshana shine in this role that was created for her. So it's scary, and it's also super exciting. And I'm thrilled and also honored to be able to step into something so special and put my twist on it." She then adds, with her characteristic playfulness, "I happen to be from New Jersey. I mean, this could be kismet!"

Visit CarnegieHall.org.