What if you found out Criss Angel, David Blaine and Ricky Jay weren't illusionists or sleight of hand masters at all — that what they were doing was real?

That's the sort of realization fans experienced when watching Irishman Rory Gallagher play guitar. In addition to his flamethrower performances, the Cork-born Gallagher, who died in 1995 at the age of 47 after post-surgery complications, was also a thoughtful singer-songwriter who infused wit and narrative into the oft-tired blues-rock format. And perhaps more importantly, Gallagher's genuine kindness and humble spirit made him a cultural hero throughout the U.K. and Europe.

Given all that, it's hard to think of even one question Gerry McAvoy hasn't been asked about Gallagher. For two decades, McAvoy, a Belfast-born bassist, toured the world as the longest-serving player in Gallagher's band — very much an aide de camp — and he appeared on all 14 of the albums released during the artist's lifetime.

He also wrote a well-received book called "35 Years Riding Shotgun" that in large part chronicled his time with Gallagher, and now, with Band of Friends, McAvoy is on the road doing a "Celebration of Rory Gallagher" tour. Also in the band are drummer Ted McKenna, who spent five years with Gallagher, and Irish guitarist Davy Knowles, a player who can not only recreate seminal parts and vocal lines, but can also provide a strong and distinct sense of improvisation and energy that takes the music beyond mere replication.

It is not a shock when McAvoy is asked about the decision to tour with a Gallagher show now. After all, Band of Friends, which formed in 2010, has been doing fine as a separate entity. With original guitarist Marcel Scherpenzeel, they released two albums of original material — "Repeat After Me" and "Too Much is Not Enough" — headlined festivals throughout Europe, and won Best Band at the 2016 European Blues Awards ceremony.

"Actually, I moved to France from Ireland in 2007. At that point, I'd spent several years playing in the (well-established blues group) Nine Below Zero, and I was unpacking boxes of records and came across the Rory albums," McAvoy says by phone from Florida, as Band of Friends heads up the eastern seaboard on a swing that includes a show Sunday in Old Saybrook's Katharine Hepburn Cultural Arts Center. "I hadn't heard them for a long, long time. And I played them. They were so great, and, you know, just remembering those days, I thought, 'It would be fantastic to do that again.' So the idea was in my mind."

Gallagher's discography is a treasure with studio standouts such as "Deuce," "Tattoo," "Calling Card," "Photo Finish" and "Blueprint." His material capably bounced from riotous electric strut ("Walk on Hot Coals," "Cradle Rock," "Shin Kicker") to genre-sustaining blues homage (Muddy Waters' "I Wonder Who," Lead Belly's "Out On the Western Plain," J.B. Hutto's "Too Much Alcohol"); from savvy pop ("Calling Card," "Moonchild," the iconic "Tattoo'd Lady") to wistful melancholy ("A Million Miles Away," "If I Had a Reason").

It's well known, though, that Gallagher never felt he could capture in studio the live energy and dynamics of the concert stage. This perhaps explains why "Live in Europe 1972" and "Irish Tour '74" are acknowledged as two of the finest in-concert albums ever made.

McAvoy particularly remembers "Irish Tour '74," which was recorded at the height of The Troubles in Belfast. The IRA was detonating bombs throughout the city, many concerts were postponed, and a growing list of artists refused to tour there. It was Gallagher's opinion, though — and it's been widely reported — that it wasn't the kids' fault, and they deserved to hear and see music. Accompanied by a film crew and mobile recording unit, the Gallagher band went into Belfast and played.

"It was absolutely exhilarating to see the crowd reactions," McAvoy says. "They were elated that we would make the effort. There was certainly an element of fear, but Rory was transcendent and we all fed off that energy. It was something I'll never forget."

With all of this history, it would seem odd for McAvoy and Mckenna, in Band of Friends, to act as though there were no Gallagher connections. From the beginning, then, concerts always included a Gallagher song or two, and the "Too Much is Not Enough" album closed with an arrangement of "If I Had a Reason."

But it was only in the past year or so that the idea of hitting the road with a show specifically dedicated to Gallagher took form. And McAvoy is quick to point out they're calling it a "celebration" rather than a "tribute."

"There are a lot of bands doing Rory Gallagher tributes that have mastered the note-for-note aspects, and that's a good thing. Anything that helps keep Rory's music alive is important. But Rory would never have just played the songs exactly the same way. Every night was new and different. We never knew what might happen," says McAvoy.

The fact that McAvoy and McKenna gleefully navigated hundreds of shows as Gallagher's rhythm section obviously provides a huge sense of authenticity and innate musicality to the cause. But the pair also knew that an artist like Knowles was perhaps even more important. He is, after all, channeling the icon around which the whole idea is based.

"Davy's not Rory, and no one will ever replace Rory," McAvoy. "Part of his brilliance was what he created onstage. Davy brings that passion and spirit to what we're doing, and it's a joy to watch. To bring those songs back so people can experience them — albeit that Rory's not there — is a sort of mission, and it had to be special for Ted and I to do this. Davy brings that."

Part of the fun of this tour, McAvoy says, is that it has provided him with the opportunity to regularly reflect on Gallagher as a friend and human being. "Rory loved life," he says simply. "We toured a lot — A LOT — and I particularly remember the early days and the sense of discovery. If we had a day off, we'd go to pawn shops to look at instruments, or have a couple of beers, or just explore a city. And we saw a lot of movies; Rory loved detective fiction and film noir."

He pauses and laughs. "I think back on recording the first few albums. We'd be still on tour and come offstage and go straight to the studio and record till dawn. Of course, we were young men, and we could do that. We can't stay out all night anymore, but I think we can certainly celebrate with the music."

Band of Friends, 7 p.m. Sunday, Katharine Hepburn Cultural Arts Center, 300 Main St., Old Saybrook; $35-$38; 1-877-503-1286, thekate.org.

Editor's note: This version corrects the name in the ending information paragraph.