This week's Utah Symphony concerts would be a capital-E Event even if they weren't Keith Lockhart's last as music director.

Leonard Bernstein's "MASS: A Theatre Piece for Singers, Players and Dancers," featuring more than 200 performers, is a once-in-a-generation experience, said Utah Symphony | Utah Opera vice president of artistic operations Jeff Bram.

"It's a life-changing and thought-provoking work," Lockhart said. "It's big and sprawling and a little messy. Is it perfect, no, but it is an extraordinary work."

"Mass," commissioned by Jacqueline Kennedy Onassis for the opening of the Kennedy Center in 1971, loosely follows the liturgy of the Roman Catholic Mass, with additional passages in English and Hebrew. The musical language is "all over the place," said stage director Michael Scarola. "Classical, jazz, blues, rock, pop -- you'd think it would be a hodgepodge, but it's so seamless." Scarola conceded that "parts of it, musically, are a little bit dated, but I embrace the flaws; I don't try to downplay them."

"Mass" will be "completely staged," with the orchestra onstage, Scarola said. The Abravanel Hall stage has been extended 12 feet and the first six rows of seating taken out. There is no set, "but ramps and platforms suggest a setting," the director said. "There is some semblance of costuming -- vestments, street clothes, robes."

The work's frank depiction of a crisis of faith caused it to be "tagged as pure blasphemy" at its premiere, Bram said.

"It's the complete antithesis of blasphemy," said Scarola, for whom "Mass" is a signature piece. "It's one of the most faith-based pieces." The moment when the Celebrant, the central figure in "Mass," breaks the chalice can be "viewed as a sacrilegious moment," said Scarola, who grew up Catholic. But it's actually "a man reaching rock bottom of what he always thought he was." But he comes through the experience ready to rebuild: "No doubt the Celebrant's faith is different, but there is faith there again."

"There will be people who don't understand that and assume it's Keith being irreverent," Bram added. "That's absolutely not his intention. It's not a Catholic piece, it's not a Mormon piece, it's not a Jewish piece -- it's a spiritual piece."

"As a Catholic, I can see how people would be really upset," said tenor Robert Breault, who will be part of the 12-member Street Chorus. "It deconstructs the Mass in a '70s way. It's fun for certain reasons, illuminating for others -- it's definitely a piece of the '70s."

"It is life-affirming and faith-affirming," Lockhart said. "Faith shouldn't be easy."