Unlike many bands, Barenaked Ladies actually relishes the moments in concert when things don’t go exactly as planned, according to guitarist and lead singer Ed Robertson.

“We’re always ready to stray from the set list and embark on a strange musical journey,” Robertson wrote in an email interview. “To me, that’s what makes the shows unique, and challenging … [it’s] the moments of improv that I live for. It’s a tightrope walk that is so fun and challenging.”

No two tours are everthe same and no two concerts are ever the same, he said.

“Every BNL show is a new experience,” Robertson said. “We leave a lot of room for spontaneity and improv. We always try to play the songs that people want to hear and throw in a few off the beaten path, but there are always new moments in every show.”

Barenaked Ladies perform July 23 at the Foellinger Theatre.

There have been two distinct phases in the life span of Barenaked Ladies: The Steven Page Period and the Post-Steven Page Period.

In 2009, lead singer and band co-founder Page left Barenaked Ladies in the wake of a drug-related arrest.

Despite the most obvious controversy swirling about at the time, Robertson has said that Page’s leave-taking was not attributable to any single factor.

A lead singer’s exit can be pretty rough on a popular band because departing lead singers tend to take a lot of a band’s signature sound with them.

The remaining members of Barenaked Ladies were anxious about how Page’s absence would be processed by the fans, but Robertson said they took it in stride.

Both Page and Barenaked Ladies went on to produce critically acclaimed new music, so there were happy endings all around.

Over it’s three-decade existence, this Canadian band has moved more than 14 million units (aka “sold albums”), won eight Canadian Grammys (aka Junos) and provided the theme for the hit TV show The Big Bang Theory.

The latter accomplishment might have earned it as many detractors as admirers, but let’s not explore that.

The band’s biggest hits (“If I Had a Million Dollars” and “One Week”) are quirky and lightweight – lyrically dexterous but goofy.

But Robertson said there are serious moments on stage as well: The song “Moonstone,” for example, which is about his mother.

Even when the band is playing silly songs, Robertson said, the musicianship is serious.

The band enjoys challenging itself. It added an acoustic set to dates on last year’s tour, and it recently participated in an album-length collaboration with The Persuasions, a Brooklyn-based a capella group that first formed in the 1960s.

The two groups met at a Lou Reed tribute show and hit it off. They subsequently moved with alacrity into a studio to see what would develop.

What developed were 15 tracks in a day and a half, Robertson said.

“I thought we were going to get three to four songs done,” he said. “It was one of the easiest recording projects we’ve ever done … [it] was such a pleasure to collaborate with those guys. They really dug in to the songs and had fun with the arrangements. It was a blast. I’m super proud of that record.”

Allmusic.com called the resulting record (Ladies and Gentlemen: Barenaked Ladies & the Persuasions) one of “the more unexpected but utterly likeable Barenaked Ladies releases.”

Barenaked Ladies hits covered on the album “are broadened and given added poignancy by the framework of the Persuasions’ deep harmonizations,” according to the review. The album works “because of the sheer joy and immense talent on display by both groups.”

Robertson said that his only goal for himself and his fellow band mates at this point is to find new challenges – the sort of challenges that are entertaining for fans, of course.

“Is that a crazy goal?” he said. “I would pay to get to play the shows we get paid to do. It’s an incredibly fortunate position to be in, and I don’t take it for granted.”

Robertson didn’t say so explicitly, but other of his personal goals must surely involve “playing the silver ball,” as Pete Townshend wrote.

He has become known far and wide as a pinball aficionado – a collector, restorer and player of vintage pinball machines.

On tour, Robertson said he usually goes off on pinball-related side trips to visit like-minded collectors and dealers.

He said the connection between pinball and music is more obvious than it might seem.

“Pinball is rock n’ roll under glass,” he said, “so the connection is pretty immediate. It’s lights and sound. Kinetic energy. Structure and chaos mixed. I can’t get enough of either!”

Robertson believes playing pinball actually improves his cognitive functions.

“The challenge of the physicality of the machine mixed with the complexity of the rule set is a great mental work out,” he said.