Chorus rises to challenge:

The Harvard-Radcliffe Chorus (HRC), with its 130-plus members drawn from Harvard students, faculty, staff, and the community at large, is not the University’s most elite musical ensemble. Founded in 1979 as a training choir for students aiming for some of the more selective choral groups, it continues to serve that purpose while also catering to its many members for whom a lower-key musical experience fits the bill.

But don’t expect holiday greatest hits or “lite” classical fare for this ensemble’s upcoming concert in Sanders Theatre. Instead, the Dec. 8 performance serves up a musically challenging, dramatically thrilling offering of William Walton’s cantata “Belshazzar’s Feast.”

“It’s Walton’s centenary,” says conductor Simon Carrington of the fellow Englishman. “I thought somebody in Boston should do it, so why not me?”

Born in 1902, Walton, along with Benjamin Britten and Sir Michael Tippett, is considered a lion among Britain’s major 20th century composers. “Belshazzar’s Feast” is one of his most notable works, combining double chorus, baritone solo, and large orchestra to tell the biblical story of the fall of Belshazzar.

“It’s pretty powerful Old Testament blood and thunder,” says Carrington, adding that jazzy rhythms make the work one of the most colorful of the 20th century choral repertoire.

But it’s not easy to sing.

“This is very diverse and very fast moving. You’ve got no time to rest,” says Carrington, himself a lean man in perpetual motion, interrupting one conversation to shout good-natured instructions at a student and apologize to a stagehand for a scheduling mix-up. “That’s a bit alarming for people who are used to singing hymns in church,” he says.

Carrington, who is acting conductor of the HRC this year while conductor Constance deFotis is on leave, brings impressive credentials to this demanding work. He was founder, member, and co-director of the acclaimed British vocal ensemble The King’s Singers for 25 years and is now director of Choral Activities at New England Conservatory.

Working with choristers who make learning or teaching or managing – not singing – their profession, Carrington makes minor adjustments in his direction, letting the singers rely on the piano accompanist to learn pitches, for instance, instead of insisting that they sight-read all the music.

“I threw them a massive challenge,” he admits. “But they have responded with energy. They’re rising to the challenge.”

Count Sheila Connelly, assistant director of M.B.A. registrar services at Harvard Business School and a soprano with the Harvard-Radcliffe Chorus for six years, among those who are meeting Carrington’s charge. “It’s exciting and it’s rhythmically challenging. It’s been great working with Simon,” she says.

In rehearsal, Carrington is patient and encouraging, albeit demanding. He makes clear his expectation that the singers extend themselves to give the work their absolute best.

“Please have your pencils ready, because you will be adrift,” he warns as the chorus shuffles into place, scores open, on the Sanders Theatre stage.

With just over a week before the performance, at one of the last rehearsals before baritone soloist Philip Lima and an orchestra of 70 professional freelancers join them on the crowded stage, Carrington is fine-tuning. Sing “God” rather than “Gahd,” he coaches, pronounce a heavenly “an-jill” instead of the leaden “an-JELL.”

“We know the pitches, now tell the story. Otherwise, it’s going to look extremely strange,” he says, reminding the ensemble that “Belshazzar’s Feast” is a dramatic cantata and it’s their job to tell the tale.

Describing the evening’s concert as “short and action-packed,” Carrington will open the performance with Gerald Finzi’s “In Terra Pax, Op. 39, Christmas Scene,” which quotes familiar Christmas carols and provides a dynamic counterpoint to the Walton work.

“It’s a very gentle, reflective piece,” says Carrington. “We’ll sing two very interesting works, utterly different. One very peaceful and one full of fire and brimstone.”

While he’s pleased with the chorus’s progress with the two 20th century works so far, Carrington admits that he has taxed the singers this fall.

“It’s been fun, but this is a huge challenge. We’ve had to push pretty hard to get it ready,” he says. “I promise next semester to do something more relaxing.”

The Harvard-Radcliffe Chorus fall concert, featuring Finzi’s ‘In Terra Pax, Op. 39, Christmas Scene’ and Walton’s ‘Belshazzar’s Feast,’ is Sunday (Dec. 8) at 3 p.m. in Sanders Theatre. Tickets: $15 and $12 general admission; $8 and $6 for students and senior citizens. Call the Harvard Box Office (617) 496-2222 for details.