Trio Galilei. (Burgess Blevins)

Lt. Col. Samantha Nerove, U.S. Army, retired, remembers the day she started recovering from PTSD as the same day she stopped and listened to the music. Since being airlifted out of Iraq in September 2008 with a badly mangled ankle and severe psychological distress from close-range mortar shellings, she’d been living at Mologne House, a retrofitted hotel on the grounds of what was then the Walter Reed Army Medical Center in Northwest D.C.

Two months into Nerove’s stay, she noticed that every Friday at lunchtime, a trio of musicians — playing a harp, guitar and something that looked like a cello — had started performing in the Mologne House lobby. They developed quite a fan base: The sofas in the lobby were filled with wounded patients, their weary relatives and mesmerized children who wanted to take turns playing a spare harp. If the musicians were between songs, they’d always smile warmly at Nerove, say hello and urge her to join them.

“You couldn’t miss Sam,” musician Carolyn Surrick recalls. “She was this fit, petite blonde, but she always had her face to the ground.”

Then, one Friday there was an open seat, and Nerove took it.

“I realized that what was missing in my life was music,” she said, “It’s like there was this empty hole, and I had just shut down inside.” As she began to listen, Nerove didn’t know exactly what she was hearing – careful arrangements of 17th and 18th century music — but she knew what she was feeling, and she hadn’t felt much of anything in months. She finally started making progress in her physical therapy, and her counseling sessions. In June, she retired from the Army with 25 years of service and is now building a fashion design business out of her basement, having thoroughly reconnected with the artsy dancer she was in high school.

“I never would have gotten where I am today if it weren’t for them,” she said.

“Them” is the three dedicated musicians in Trio Galilei: harpist Sue Richards, guitarist Ginger Hildebrand and Surrick, who plays the viola de gamba, a forerunner to the cello. Nerove is one of thousands of soldiers who have stopped to listen, and while only a handful have kept in touch or booked the musicians to play at their retirement parties, as Nerove did, there is broad agreement at Walter Reed that what the musicians have done is remarkable, and has been integral to the recovery of many wounded servicemen and women.

“There are all sorts of things happening here at Walter Reed intended to help the troops. All of them are well-intentioned, but not all of them work,” said Arthur Bloom, a Juilliard-trained pianist who runs MusiCorps, a nonprofit music mentoring program at the hospital. “Five years ago, if you would have said, ‘How about playing early music, in a barracks, for severely injured 25-year-old guys?’ I might have said they were out of their minds,” he said. “But it works. It really works.”

Many musical guests come to Walter Reed, now located in Bethesda — but most, including the likes of Yo-Yo Ma, play only one-off gigs. And then there are the bagpipe brigades, which jar the war-addled ears of soldiers not ready to be bombarded by “Amazing Grace.” “They nearly gave me flashbacks,” Nerove recalled, shuddering.

Trio Galilei “works” because they are quiet, they are here every week to form relationships, and they are amazing musicians, Bloom said. “People want to hear good music, not schlock, and you don’t have to have gone to Juilliard to recognize schlock.”

The trio specializes in 17th and 18th century music of the British Isles. Although she plays a replica of a period instrument, Surrick admits that they are more concerned with crafting artful arrangements than reconstructing historical performance methods. She and Richards also play in Ensemble Galilei, a ­Celtic-leaning early-music group that has performed in 46 states. Whenever possible, they ask presenters who book them to also include an outreach gig at a Veterans Administration hospital, and they pack giveaway copies of Trio Galilei’s two CDs.

Surrick, Richards and Hildebrand were only a few months into their Walter Reed performances when they started getting requests that, taken out of context, sounded like insults.

“Can you come back at night?” soldiers suffering from PTSD would ask. “I can’t sleep.”

They couldn’t. But they could make recordings. Surrick called the team of engineers and designers who Ensemble Galilei typically pays to produce its albums. Everyone agreed to help with the Walter Reed project for free. “Above and Beyond,” the first album, featured traditional Irish and British tunes, plus music composed in the 1700s by Bach, Gaspar Sanz and Turlough O’Carolan. In August, they began giving away copies of “Home,” which added Telemann and a traditional American song to the repertoire.

Surrick estimates that they’ve passed out more than 4,000 copies not only to troops, but also to Walter Reed staff. VA employee Russ Gilmer is a typical beneficiary. On a recent December afternoon, he picked up a burger and onion rings and made a beeline for the table closest to where Richards and Surrick were playing. Between bites, Gilmer described himself as a Celtic music fan who spends his days processing soldiers’ medical claims. “In this job, when I get a chance to unwind, I need to do that,” he said. “It gets pretty stressful, but this is great.”

Whether or not to play volunteer “background music” gigs is a matter of debate among professional musicians. Add the Trio Galilei’s connection to the military, and you have a combustible conversation topic for left-leaning circles. Some people just aren’t comfortable with how fervently the musicians describe their work at Walter Reed, an institution that has not been without well-publicized problems. As an apolitical compromise, Surrick encourages musicians to seek out standing gigs playing at nursing homes, hospitals or prisons.

“If you are playing at a high level, your practice is pretty awesome, you can take your practice, and you can do it someplace where it can do some good in the universe,” Surrick said.

As a warmup for their annual Washington-area holiday tour, five members of Ensemble Galilei played at the Warrior Cafe on Friday. This season, they’re performing arrangements of carols from the 13th through 19th centuries, including some from their ethereally titled new album “Surrounded by Angels.” After performances in Takoma Park and Annapolis, the tour concludes Sunday evening with a free show at the National Gallery of Art. The other five regular members of the ensemble — who play flutes, recorders, violins and percussion — are scattered across the country, so in that earlier week’s performance at Walter Reed, Richards and Surrick were a duo. As they packed up their instruments, a young soldier who had been listening came forward. One hand was clutching a cane, the other a book of Surrick’s poetry. He noticed that her instrument case was covered with stickers representing military units, including the Navy SEALs and Army Rangers.

“I’m only an artilleryman, but would you sign this?” he said. She did, and as he limped out of the Warrior Cafe, there were tears in his eyes — but he was also, just barely, smiling.

Ensemble Galilei

Sunday at 6:30 p.m. National Gallery of Art, West Building, West Garden Court. Free.