With the holiday season just around the corner, Pentatonix are ready to kick off their second Christmas special, “A Very Pentatonix Christmas”, with special musical guest Jennifer Hudson.

Speaking with ET Canada at the annual unveiling of the Hudson’s Bay and Saks Fifth Avenue holiday window display in Toronto, the members of the famed a capella group — who just released a deluxe version of their second full-length holiday album, “A Pentatonix Christmas” — open up about their work with the Grammy- and Oscar-winning artist.

Related: Former Pentatonix Singer Avi Kaplan Forms New Group, Covers Outkast’s ‘Hey Ya!’

“It’s always so humbling and very, very exciting that people like Jennifer Hudson [have] heard our music and they know who we are,” says tenor Mitch Grassi. The group’s baritone Scott Hoying adds, “I was such a huge fan and so, for years later, for us to be performing with her on a Christmas special, […] it’s hard to describe. It’s a bit surreal.”

For their upcoming holiday special, which will also feature show appearances by Jay Leno and ventriloquist Darci Lynne Farmer, Pentatonix will unveil a slightly new sound following the departure of their fifth member and bass, Avi Kaplan, who left the group this past May.

Related: Avi Kaplan Announces He’s Leaving Pentatonix: ‘The Hardest Decision I’ve Ever Had To Make In My Life’

Addressing Kaplan’s choice to leave, Hoying says, “He came to us. He sat us down. [He said,] ‘Here’s the issues I’m having in this group and I think I have to take a step back for my own mental health. I have to slow down. I can’t keep up with this pace.’ And we were like, ‘We totally respect that. There’s no bad blood.'”

While Kaplan’s departure was a surprise to fans, Hoying confirms that the rest of the group were well aware of his intentions. “He talked to us early about it,” Hoying says. “We’re just so happy that he’s doing what he needs for himself because I think that’s the most important thing.”

Related: Dolly Parton Teams Up With Pentatonix For ‘Jolene’ Remix

In early October, Pentatonix announced the addition of singer Matt Sallee, who will join the group on their holiday tour. “He is a bundle of joy and he’s just so excited to be doing this with us,” says cello Kevin Olusola. “We really, really love working with him.”

Speaking about the audition process, Hoying adds, “We took in audition tapes from people around the a capella community in the bass world and watched 40-50 people that were really great and met with eight of them.” He continues, “Matt stuck out as he had the whole package — the energy — like everything about him just really clicked.”