“All it takes is two people to have an Irish session,” says fiddler Rose Clancy of Chatham, who has been hosting Celtic jam sessions in pubs and restaurants on Cape Cod for more than 15 years. Her regular gigs at the Squire in Chatham have been on hold while the restaurant was being renovated, but they are starting up again this week with a special St. Patrick’s Day session from 6 to 9 p.m. She hopes to resume regular sessions there in late April.

A few weeks ago, I joined Clancy and fiddlers Heather Swanson and Sara Piazza, accordionist John Alden, and guitarist and singer Max Cohen for a session at the Red Nun Bar & Grill in Dennis Port, where Clancy plays every Saturday from 5 to 7. I was there just to take photos, but the music was infectious. They were only three tunes deep when Clancy declared, “You should have brought your fiddle!” and I had to admit it was waiting in the car, just in case.

At an Irish session the players sit in a circle. That way, they can better hear each other, watch for fingerings and bowings, and take signals from whoever’s leading — in this case, Clancy.

Fiddlers, mandolinists, guitarists, and tin whistle players come with a memory bank of traditional Irish tunes, usually learned from other musicians at sessions. If they don’t know the tune, they improvise.

Clancy’s Catholic parents moved from Armagh, a city in predominantly Protestant Northern Ireland, to the Bronx in the early 1960s. “My father was making a living as a musician when he first came to this country,” she says, “so there were a lot of musicians around my house, and I heard a lot of Irish music. I knew probably when I was three or four that that’s what I wanted to do.” She started lessons in classical violin in elementary school. “I was obsessed with it,” she says.

Clancy’s father, Gene, who plays the guitar, formed the Irish Ramblers with his brothers Pat and Brendan. Rose was scared of performing, but Gene encouraged her. “He would say, ‘Come on, Rose, let’s go. It’s gonna be great,’ ” she says. “He pushed me forward. And I’m very grateful for that. Because if he hadn’t, I’m not sure that I would be able to perform today.”

Her family owns Clancy Relocation & Logistics, a residential and commercial moving business where Rose worked for many years until one day, at age 42, she “just quit and went to violin-making school in Boston.” Eleven years ago, after graduating from the North Bennet Street School, she moved to Chatham and founded the Chatham Fiddle Company, where she makes violins and gives lessons.

The Irish music scene on the Cape is “very forgiving,” she says. “You don’t have to do everything perfectly.”

No one is quite sure how that scene here got started more than 30 years ago, but one of the instigators was Billy Hardy of Eastham, founder of the Cape Cod Fiddlers.

“Back in 1989,” says Hardy, “I started calling all the fiddle players I knew on Cape Cod and invited them to come to my house once a week to play some music.” Among his group were Hardy’s partner Beth Sweeney, Louise Paquette, Lou Roten, Richard Huttinger, Chris Miner, Dan Freitas, Stuart Moore, Dinah Mellin, and Denya LeVine.

LeVine, who hosts the WOMR-FM show The Fiddle & the Harp (broadcast Mondays from 5 to 8 p.m.) with Dinah Mellin, had moved to Wellfleet in 1980. She started hosting sessions at the First Encounter Coffee House in Eastham and then at the Bookstore & Restaurant in Wellfleet.

“It wasn’t too much of a scene,” says LeVine. “It was just starting.” When the group relocated to the Olde Inne (now O’Shea’s Olde Inne) in Dennis, Clancy was introduced to the Cape Cod Fiddlers.

Many Irish sessions have been happening in Dennis Port at the Red Nun and at Buckies Biscotti & Bakery Café just next door. But this summer LeVine hopes to revive a session she hosted last year at the Flying Fish Café in Wellfleet. And Hardy still hosts sessions on Monday nights at his home in Eastham.

This music has been passed down through generations at these sessions, and interest in Celtic music seems only to growing.

“Today, we can find written music and teachers anywhere in the world on the internet,” says Clancy. “It’s fabulous.”

Jigging and Reeling

The event: St. Paddy’s Day Irish music session with fiddler Rose Clancy
The time: Thursday, March 17, 6 to 9 p.m.
The place: The Chatham Squire, 487 Main St.
The cost: No cover