The mega-selling operatic quartet Il Divo faced a double-edged sword of success with a three-year whirlwind of sell-out concerts and hit albums from 2004 to 2006.

Yet each accolade brought with it greater demands, leaving the group road weary and close to burnout by the time it finished touring behind 2006's Siempre.

"I wouldn't necessarily call it burnout per se," American tenor David Miller says, alongside Spanish baritone Carlos Marin during a Canadian promotional stop. "I mean, the batteries were running low. We were just going, going, going because every success kept opening doors for more success. And you really can't say, 'No, no thank you. That's enough success. I'm good.' "

The group, formed by American Idol patriarch Simon Cowell in 2004, took a year off before joining forces again for its new studio album, The Promise, a release Marin says finds the group coming into its own despite opting to cover and rework ABBA's The Winner Takes it All (Va Todo Al Ganador).

"For the first time -- I mean it's not the first time -- but we had a lot of fun on this album because we chose not obvious Il Divo songs such as (Leonard Cohen's) Hallelujah (Aleluya) and The Power Of Love (La Fuerza Mayor) by Frankie Goes To Hollywood. But it was the first time we really felt like we were a unit.

"We didn't know if the people would like it. And I think that therefore this album is the most mature because we just chose not the really obvious songs."

Il Divo, which also includes Sebastien Izambard and Urs Buhler, came into The Promise with a list of more than 200 songs from which to choose.

"The four of us have a list, Simon has a list, our mothers have a list," Miller says. "Everybody's got a list of what they want to hear and it's all valid.

"It just becomes a question of finding those songs that are not obvious but have the potential to be within the Il Divo framework. There's a lot of songs with great melodies that have nothing to do with romance -- so that eliminates them, in a sense."

Another part of Il Divo's blueprint to success is deciding who is doing what during the verses and chorus in each song. With four powerful voices each vying for limited space, Marin says it was initially a bit unnerving for all involved.

"It was a huge challenge for us each coming from our own solo career and then suddenly Simon put us together and boom. The huge challenge was also singing with other fantastic singers and it was a big challenge for myself as a big ego, operatic thing.

"It was tough in the beginning because obviously we didn't know each other and when you don't know each other it's like, 'Okay, what's this guy going to sing? Is he going to sing my part?' But now it's amazing, we're just going so well and it's just so easy."

Perhaps the only sticking point now with finding that often elusive key to success is trying to change or breathe new life into the process, something Miller believes is quite difficult to tinker with.

"It's a tough thing because there is kind of an Il Divo formula and we don't like that there's an Il Divo formula," he says. "But when we do it, not with the formula, with the sharing and a certain order of things, it doesn't sound like Il Divo. There's no cohesion with that. Most of the songs on The Promise do fall into the formulaic system, but it is the system that's the most powerful for us. So we go 'Arrgh' -- but it works."

Il Divo performs an extensive Canadian tour starting in late April which includes stops in Ottawa (May 2), Toronto (May 5), Winnipeg (May 22), Edmonton (May 25) and Calgary (May 26).

"We're doing Toronto, Montreal, London, Calgary, Quebec," Marin says.

"Quebec is a province, we're not doing all of Quebec," Miller adds with a laugh.

On and on and on with the show

Il Divo's upcoming world tour will be different in a number of ways, perhaps the biggest change being the length of the shows.

According to Il Divo members Carlos Marin and David Miller, the plan is to perform seven songs from The Promise in a set that will be some 25 songs in length.

"It's going to be a long show," Marin says.

"Our last show was 17 songs, so we've expanded it considerably to what we're wanting to achieve," Miller adds.

The group also says the songs off The Promise aren't too arduous to execute in concert.

"I think we specifically make choices based on how it's going to sound on the album and try as best to keep the idea that, 'We're going to have to do this live as well,' " Miller says. "So maybe we don't want to have the key that high, maybe we want to take it down just a little bit.

"There's been some butting of heads about that because when we're making an album, it should always be about the album, it shouldn't be about, 'Well, what are we going to do when this happens?' "

Miller also says that the long break the foursome took before The Promise will give them the energy to produce many more albums and tours before taking another long break. "It's the best way to keep things healthy and moving forward."