It was a fittingly ceremonial start to the inaugural concert of this new semiprofessional chorus, launched this year by former Choral Arts Society of Washington director Scott Tucker and producer, composer and music director Nolan Williams Jr. It was also a standing-room-only affair, with more than 700 tickets sold and attendees hugging their own coats to make room.

As co-artistic directors, the two men have made it the WDC’s explicit mission to “celebrate the rich tapestry of musical styles that stem from both Black and White traditions.” On Sunday, they also made it their mission to celebrate the season with “Noel! A Glorious Mystery,” a program of holiday hymns, choral deep cuts, festive contemporary experiments and attention-seizing fresh arrangements of old favorites.

“If you didn’t come here in the holiday spirit, you’ll leave in the holiday spirit” host Allison Seymour said at the outset. “You might even buy a tree on the way home.”

The program opened with a churchwide singalong of composer and organist Evelyn Simpson Curenton’s arrangement of “O Come, All Ye Faithful,” which put the sublime half-diminished seventh made famous by David Willcocks to chill-inducing use, and concluded with a stirring bespoke coda.

Pipes properly cleared, the chorus then moved straight into Daniel Pinkham’s 1957 “Christmas Cantata (Sinfonia Sacra).” Accompanied by a small brass ensemble, they beautifully handled the softly sustained “Alleluia” of its opening movement, the veil of soprano and alto voices in its central “Adagio,” and the sprightly and celebratory “Allegro” finish.

Baritones Daniel Smith and Darrick Speller were highlights of the show’s second chapter, which paired Margaret Bonds’s “Could He Have Been an Ethiope?” (with its unexpected harmonic destinations) and Peter Cornelius’s “The Three Kings.” Speller’s welcoming warble was especially suited to the narrative role of the lyric.

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The intricacies of Francis Poulenc’s “O Magnum Mysterium” offered a demonstration of how finely tuned this young chorus is. A lushly layered “Ave Maria” from the early-20th-century Black composer Nathaniel Dett was radiantly realized by the chorus and splendidly decorated by tenor Devin Mercer.

The penultimate portion of the program opened with Renaissance composer Jan Pieters Sweelinck’s perennially popular motet, “Hodie Christus Natus Est,” but this austere a cappella gave way to a showcase of alluring contemporary arrangements. A muted trumpet cracked the door for a sleek and cosmopolitan “Silent Night” arranged by Williams Jr., narrated by Aaron Myers and gracefully sung by bass David Breen, who strung its melody like a strand of lights over slowly unfurling jazz-hued harmonies.

The soprano Jouelle Roberson was the jewel of an energizing suite that recast “O Holy Night” in progressively richer and more robust settings, reaching a gospel-infused climax that had my fellow listeners swaying in the pews. Williams Jr.’s smart and shadowy arrangement of “What Child Is This?” offered soprano Michelle Maxwell a forum for her buoyant, vibrant vocalizations, and the chorus a chance to sound supremely slick. A final “Glory to God!” section landed with Mark Butler’s arrangement of “Glory, Hallelujah to the Newborn King,” mightily led by tenor Wayne Jennings and concluding in a toe-curling hail of praise. And a finale of a Williams Jr. arrangement of “Gloria!” (i.e., “Angels We Have Heard on High”) with blazing performances from tenors Michael McKeon and Jonathon Hampton.

It wasn’t a perfect performance — the balances were here and there a bit off and unruly, which could have had as much to do with the venue or the microphones onstage as the inexperience of the chorus itself. Also, next time, someone needs to remember to disengage the snare drum, which caught some resonant and thus rattling frequencies at inopportune times.

But in a town nearly drowned in choral talent, the WDC immediately shows a special spark — a fearless mix of old and new, classical and not, expected and un-, performed with skill to match its vivacity. I won’t lie: As I rode home past the Christmas tree stands on Massachusetts Avenue, I considered asking my Lyft driver whether he had any twine in the trunk.

The Washington Douglass Chorale won’t make its next appearance until spring, an April program titled “Liberty and Justice for All?,” which will put an emphasis on the question mark and include works by Duke Ellington and William Billings. I’d recommend stalking the site and securing tickets in advance; this WDC is a glorious mystery no more.