SALT LAKE CITY — Growing up singing in small choirs in western Oklahoma, actress Kelli O’Hara never imagined she would one day perform in front of the Tabernacle Choir at Temple Square.

“This is the ultimate invitation, isn’t it?” O’Hara said at a press conference Thursday. “The chance to sing in front of a live orchestra of this caliber with the voices of 365 singers led by this man (Mack Wilberg), I think anyone would jump at the chance, and I just happened to be the lucky one this year that was asked, and I wanted to move mountains to make it work.”

O’Hara, who has received seven Tony nominations and performed with the Metropolitan Opera, and actor Richard Thomas, known for playing John-Boy on “The Waltons” TV drama, will perform as the guest artists at the Tabernacle Choir’s 2019 Christmas concerts Thursday through Saturday at the Conference Center, a venue Thomas called “astonishing.”

“For a greedy actor, it’s heaven,” Thomas said. “The spiritual aura of the artists, of the venue, of the seriousness of intention behind the work, is really palpable, and it’s just thrilling to be a part of it because I feel that I will be able to plug all of my love of Christmas into this experience.”

Thomas said “it was like Christmas” when he was asked to perform at the concerts.

“We had LPs of the choir in our home when I was a boy growing up, and the Christmas music that the choir sang was just a part of all my childhood Christmases, so one feels a connection wherever you are with this extraordinary musical organization,” Thomas said.

“Also, I have to say that when I was told that Kelli was going to be the other guest artist, I just was so excited because she is the preeminent singing actress of our time in the American theater,” he added.

Wilberg, music director of the Tabernacle Choir and Orchestra at Temple Square, said they are “very, very honored” to have O’Hara and Thomas with them.

“We’ve tried to capitalize on the remarkable gifts that are unique to them, and I have to say, after going through the program last evening for the first time, I think that everyone will leave feeling like they’ve been well fed by the many things that they’re going to hear,” Wilberg said.

Guests at this year’s concerts can expect to hear old Christmas favorites as well as some music they probably haven’t heard before, including one piece that is particularly meaningful to O’Hara, according to Wilberg.

More than 60,000 people each year view the live concerts, which are later broadcast to millions on TV. Working on the performances is a constant process, with more than 1,000 people — many of them volunteers — involved in the production, according to Ron Jarrett, president of the choir.

How the Tabernacle Choir Christmas concert became a national tradition

“It is a great blessing to the community here in the Wasatch Front for the leadership of The Church of Jesus Christ of Latter-day Saints to provide a beautiful facility, to turn the lights on, and to have this type of quality and experience that is available each year,” Jarrett said.

O’Hara said many of the Christmas concerts’ previous guest artists are good friends of hers.

“We’ve chatted and people always say it’s an extraordinary opportunity and experience,” O’Hara said. “There’s a very positive spirit and energy here, and it is beautiful at this time of year, and anytime really. It’s enlightening.”

Thomas said he thinks there is a connection between his character John-Boy and the event “in terms of the humanity and sense of caring and love and empathy, which is very much a part of his character and which I think just fills the building during the performance.

“My wife was watching them in the rehearsal last night, and she said to me in the room last night when I got back, she said, ‘You know, that theater is full of angels. It’s full of angels. They’re everywhere,’ and it feels that way,” Thomas said.

O’Hara complimented the choir on its training, discipline and technical ability and praised the set’s attention to detail.

“I grew up singing in the choir in church and at Christmastime always and these particular songs in a way that made me feel like that was my purpose, and that’s why I’m here,” O’Hara said.