CIAO CEAUSES¸CU Florentina Ramniceanu, far left, escaped from Romania to the States in 1980.

As the miniscule audience for chamber music continues to wither away, the plucky classical gangs have become an endangered species. To stay in the black, these small ensembles depend on a devoted band of donors and groupies and must be that rare breed of musician: versatile, constantly imaginative and masters of their instruments. The overlooked all-female Orion Ensemble has survived locally for 15 years, and now it’s fighting for another 15.

“What sets us apart is an incredible commitment to making it no matter what,” says Orion violinist and cofounder Florentina Ramniceanu. She’s prepping for the quintet’s last anniversary concert of the season, held at Roosevelt University on Wednesday 21. The Romanian forged the group as a trio in 1992 with pianist Diana Schmück and clarinetist Kathryne Pirtle but soon itched to expand their repertoire and potential. A few years later, enter two additional members—violist Jennifer Marlas and cellist Judy Stone—and the unit has been inseparable ever since. When they changed management several years ago, the Orion wagon took a break from touring and stayed hitched to Chicagoland, but Ramniceanu wants to start exploring the country again.

We caught an upcoming program (already performed in concert twice in April) in Evanston; it includes a new commission called Tango, Prelude and Fugue by Northwestern grad Erling Patrick Horn. “We knew we had to play more of his music when we heard his Black Tango a few years ago,” Ramniceanu explains, adding that the piece recalls a classic dance of Argentine master Ástor Piazzolla, while the recently commissioned Prelude more closely approximates the austere stylings of a Bach fugue. Though Orion frequently commissions such works, area composers like Robert Kritz and Sebastian Huydts volunteered their services to the ensemble.

At times throughout their current program this Justice League of powerful players fractures for special missions, for what Ramniceanu describes as boundary stretching in search of a unique balance, as in Morton Gould’s Benny’s Gig, a duo for clarinet and bass where wonder-reedist Pirtle teams up with CSO bassist Robert Kassinger for an eight-part lazy-jazz essay that evokes lugubrious bayous.

That inimitable equilibrium, as Ramniceanu emphasizes, wouldn’t be complete without a warhorse of a piece. Including a storming chestnut like Schubert’s “Trout” Quintet is Orion’s way of throwing a bone to its longtime supporters, the “Orion family,” which isn’t to say Ramniceanu is reluctant to play the so-called all-time favorites. The “Trout” comes as close to a chamber hit as anything, but Orion tears into it with a zeal that’s unbound by familiarity. As the final chord of this 45-minute marathon fades and echoes through the dropped jaws in the crowd, the women on stage look at each other as if stoned on a runner’s high, eager to start the workout again.

Ramniceanu attributes Orion’s longevity to its strident devotion to chamber labor: “So many other chamber ensembles have full-time players in a symphony or somewhere else,” she says. “We gain an extra edge because we rehearse together year-round.” That’s a lot of time to spend around the same group of artists, but Ramniceanu describes this gang mentality as vital for survival, far more than matters financial or artistic: “For musicians, we really love each other as close friends, and that’s uncommon.”

The Orion Ensemble fights the good fight at Roosevelt University Wednesday May 21.