Dancers with the Gay Men's Chorus of Washington D.C. — the largest of its kind in the nation — rehearse for their December holiday concert at the New York Avenue Presbyterian Church. (Jahi Chikwendiu/WASHINGTON POST)

The dancing nuns are counting jazz squares.

On the fifth floor of New York Avenue Presbyterian Church, Craig Cipollini, choreographer and business manager of the Gay Men’s Chorus of Washington, D.C., leads a dance rehearsal for the annual GMCW holiday show.

This year’s extravaganza, “Red and Greene,” opens Dec. 16 and features Broadway’s Ellen Greene as its special guest.

The eight men in front of Cipollini are wearing jeans or gym shorts with T-shirts and sneakers, but they will be in habits come showtime. Possibly with heels, though that’s to be determined. They are practicing a song from “Nunsense: The Musical,” and are at various stages of prepared. One slides easily into a split and back to his feet again; another struggles to master the art of stepping with his right foot while swinging his left arm. Cipollini raises an eyebrow. “We need to work on your marching.”

The offending dancer nods, embarrassed. “I know.”

They continue rehearsal — From the beginning! With music! — singing the praises of convent life, where you never have to decide what to wear. “If you want to wake up and not think about your makeup, join the convent!

They introduce themselves, providing a “Merry Christmas” with “Marys by the score.”

“Sister Marry Me!”

“Sister Mary Lou Retton!”

“Sister Mary-juana!”

It is all very rambunctious, with lots of flirty winking and hip rolling and, ah, Christmas spirit.

Later that night, 220 men gather in the same room for a choral rehearsal. The mood is decidely more traditional, as they run through such holiday standards as “I’ll Be Home for Christmas” and “In the Bleak Mid-Winter,” along with “Miracle of Hanukkah.”

The evening is a microcosm of the show, which bounces between the ridiculous and the reverent.

“There’s a little bit of everything,” Cipollini said during a break from rehearsal. “There are these fun, over-the-top production numbers mixed in with well-known holiday songs.”

The almost all-volunteer GMCW (there are four full-time paid staffers) is the largest of its kind in the nation. They are a diverse group, ranging in age from early 20s to at least 70. Multiple ethnicities and day jobs are represented. “You join and you inherit 250 gay brothers,” Cipollini said. “You find people with a common background: a love of music and of being gay.”

The GMCW was formed in 1981 and has an annual audience of more than 12,000 people. Though the majority of that audience is part of the LGBT community, a growing contingent of straight-identified individuals attends shows, as well. The chorus has performed at the Kennedy Center, the National Theatre and Carnegie Hall, among other venues. Even if you think you’ve never seen the singers before, chances are you have: They performed at President Bill Clinton’s second inauguration and at President Obama’s inauguration, singing on the steps of the Lincoln Memorial behind Josh Groban and Heather Headley.

Despite the ubiquity of holiday fare in December, Cipollini is sure that the GMCW production is a unique endeavor. “At other shows, you’re not going to see men with showgirl headdresses.”

Red and Greene

Dec. 16-18, Lisner Auditorium at George Washington University, 730 21st St. NW. Call 202-293-1548 or visit