"A bouzougi," the singer and multi-instrumentalist said.
Bad answer. Fortunately for Doyle, the customs officer was in a good mood that day.
"The last thing I would ever do is try to be funny in a customs office!" Doyle told Pollstar, swearing that from now on he'd refer to the Greek/Irish hybrid instrument that's roughly pronounced "bazooka" as "a big mandolin."
Great Big Sea hails from the Canadian Atlantic seaboard province of Newfoundland, where Celtic and folk music influences are as much of the landscape as cold is to winter. A thriving live scene in the band's hometown of St. Johns is a natural, considering most families grow up with traditional music and instruments in the home.
But pop and rock 'n' roll are pervasive in the Great White North, too, and artists from Newfoundland and Cape Breton have earned a reputation for creating a unique fusion of the genres.
That influence is easy to hear in Great Big Sea, whose five members play more than 20 different instruments between them ranging from guitar, accordion, concertina, various pipes, drums and fiddles to the troublesome bouzougi.
"I don't even remember learning how to sing the traditional songs that I know," Doyle said. "You just know them. They come with the birth certificate. I barely remember learning to play guitar. They're just always around. Accordions are just always around.
"I remember learning how to ride a bike; I don't remember learning how to play guitar."
Though we usually like to showcase newer artists on these pages, Great Big Sea has been around for 11 years and is working on its ninth album with Warner Canada since 1995.
They may be Canadian music heroes, according to agent Brian Swanson of Monterey Peninsula Artists, but there's that U.S. nut to crack. And they've made a good run at it, branching out south of the border and selling out such venues as Irving Plaza, The Fillmore, and Boston's Avalon on their last American outing.
Great Big Sea's eighth album, Something Beautiful, was released in February, and the band followed what's become something of a routine by launching the support tour on the East Coast first, for maximum media effect. In April and May, they hit the West Coast, and then returned to Canada, where the band just launched another leg.
Manager Louis Thomas of Sonic Entertainment Group has been with the group for most of its existence.
"I was actually their first national booking agent, out of Toronto," Thomas told Pollstar. "They were doing Irish pub, week-long gigs. I started working them into the college and university Canadian market and getting them in good supporting situations with other artists.
"We were essentially building their ticket price and getting some real value for them, instead of so many soft ticket, pub weekends," Thomas, a former musician himself, explained.
Great Big Sea has the benefit of a full business team behind it now, including two agents - Swanson and The Agency Group's Jack Ross in Canada - and traveling road crews and tour managers. But the five-member band, including S‚an McCann, Bob Hallett, Murray Foster and Kris McFarlane, doesn't take the business end of the music business for granted.
"I'd rather be playing a concert than sitting in a lawyers meeting any day," Doyle said, laughing. "But when we started, when we were in the really fragile early stages, we learned to divvy up our duties, responsibly get to and from the gigs, and get the work done. It's important. I don't know of a single band that's been successful that doesn't do that in some fashion - to act responsibly enough to get it done.
"Bands don't break up because of musical differences, ever. They break up because somebody didn't lift their share of the cables, or somebody didn't show up, or showed up late too often, or got loaded once too often!"
Swanson appreciates Great Big Sea's work ethic, as well as their live show. He's been working with the band for just more than a year, and confesses to have been blown away once he finally saw them in Canada.
"The very first time I got to see them was when I went to Fredericton, New Brunswick. I saw them in a hockey arena with about 4,500 people in a town of about 10,000," Swanson told Pollstar. "You can really see that in a lot of ways they're kind of champions of that small town spirit," Swanson said.
Doyle spoke to Pollstar from the band's studio back in St. Johns. Even though he could have had the weekend off, he'd booked a fund-raising gig for a local church that Saturday. The upcoming Canadian trek, the sold-out American shows and European tours were far from his mind.
"I still love playing the little clubs in the fishing villages in Newfoundland," he said. "I don't think the Catholic church in St. Johns will be reporting the box office, though!"
And nobody will be trying to check his bouzougi at the door.