Joseph Flummerfelt’s Westminster Choir, the Spoleto Festival Orchestra, and assorted starry friends have rarely gone home after the festival without leaving a memorable choral-orchestral triumph in their wake. And this year’s outing should be no exception.

Of course, they get some help from local choral stalwarts — namely Robert Taylor and his Charleston Symphony Chorus. Without them, not even the WC’s 40 magnificent voices could hope to pull off the kind of rich and powerful choral sound that Flummerfelt always delivers in these big-band choral blockbusters. Good thing we can claim some classy choral talent of our own. Last year’s sublime rendition of the Brahms Requiem was perhaps their finest joint effort to date.

But an equally tempting program awaits us this time ’round, as they honor Mozart in his 250th birthday year. We’ll hear the master’s stunning Mass in C Minor, known as “The Great.” Save for his beloved Requiem, it’s his most exalted choral work. He wrote it not long after he abandoned Salzburg for the greener pastures of cosmopolitan Vienna.

There, he studied the best music of Bach and Handel, which liberated his sense of choral grandeur and taught him a thing or two about polyphony. This glorious fragment (like the Requiem, it remains incomplete) was written as a wedding gift for his accomplished bride Constanze, who sang the treacherous second soprano part at its premiere. Too bad she never nagged him into finishing it.

The smaller gem to be heard here is the lush Alto Rhapsody, by Johannes Brahms. He loved the lower musical sonorities, as we’ll hear in this sweet, molten marvel for alto and male chorus. The icing on an already rich cake will be a pair of spectacular solo arias from bel canto opera masters Bellini and Rossini.

The star solo attraction here is diva Jennifer Larmore, who will surely stand as Spoleto’s supreme big-name guest-artist coup this year. One of the world’s handful of top mezzo-sopranos, she’s sung at any major opera house you can name and has a goodly pile of prime CDs to her credit. It turns out she’s been here in Spoletos past — as a Flummerfelt protégé and member of the WC. She’ll show us how it’s done in the Mass, as she takes on Constanze’s spectacular part. Then we’ll hear the honeyed depths of her lower range in the Brahms, before she gives us a final display of vocal pyrotechnics in the two florid and dazzling bel canto arias. (Check out www.spoletobuzz.com for some further musings on Larmore and what made her come back to Charleston)

And she’ll be in terrific vocal company, with Ellie Dehn from the Don Giovanni production, who replaces Nicole Cabell (Cabell’s Roméo et Juliette rehearsal schedule conflicted with the choral rehearsals). Together they’ll dominate the solo vocals. Tenor Steven Tharp and bass Rosendo Flores are to be the very promising male soloists, but they don’t get nearly as much to sing (Mozart tended to get carried away writing for the ladies). Sorry, gents. And don’t forget the superb players of the SFO — they’re among the most unsung of Spoleto heroes.

Move fast — this one is sure to sell out pronto, if it hasn’t already. It ought to be one of the brightest jewels in Spoleto’s crown this year — but then, it usually is.

FESTIVAL CHORAL CONCERT • Spoleto Festival USA • $10-$65 • June 5, 8 p.m. • 1 hour 45 min. • Gaillard Municipal Auditorium, 77 Calhoun St. • 579-3100