If you thought the Rheostatics were bucking rock 'n' roll convention when they composed a soundtrack for the Group of Seven's paintings a couple of years ago, wait 'til you get a load of their new project.

The always unpredictable Etobicoke-born quartet -- back at Barrymore's tonight after a long absence from these parts -- is currently following in the footsteps of Raffi, Fred Penner and Mr. Dressup and putting together a children's album.

"It's kind of our version of what children's music might be," explains bassist and vocalist Tim Vesely, on the line from his Toronto home.

"It's going to be a narrated story -- narrated by a narrator who has yet to be named -- with songs that are related to what's going on in the story, with instrumental bits here and there."

Four or five songs from the as-yet-untitled children's album have recently wormed their way into the Rheostatics' sets, he adds, so fans will probably get a taste of what's coming tonight -- although it's still up in the air when the album will see the light of day.

"I think that depends on whether or not we're going to do a book to accompany it ... That will probably delay the release until Christmas or the new year," says Vesely, adding guitarist Martin Tielli -- whose artwork has graced previous Rheos album covers -- will likely provide illustrations for the book.

"We're going to try and finish the music this summer, and if the book happens it will be another six months."

The idea to do a record for kids germinated in late 1996, he says, while the Rheos were out "experiencing the huge arena-rock experience" as the opening act on the Tragically Hip's cross-Canada tour.

Feeling rather ambivalent about playing night after night to throngs of largely indifferent Hip heads, guitarist and vocalist Dave Bidini suggested the band attempt "something as far away as possible from what we're doing now," Vesely recalls.

Not that the band bears the Hip -- whose members are on record countless times singing the Rheostatics' praises (Bobby Baker once described them, rather aptly, as "maybe too good for their own good") -- any ill will.

"It's hard to imagine getting a better opportunity than doing the Hip tour," says Vesely, " 'cause they're just so nice to be working with, and their crew. We just got the royal treatment, and we were playing to a packed house every night.

"At the same time, it didn't make us any more popular than we were to begin with."

It's not likely, of course, that an album-length children's story will rocket the defiantly brainy Rheostatics into the same mega-sales orbit as, say, Our Lady Peace, either. But that would hardly seem to be a concern for a band that's shown relatively little regard for musical fashion throughout a career that now spans the better part of two decades -- not to mention every musical genre from Crazy Horse-style garage-rock to calypso to dreamy, ambient underwater "whale music."

"That's our latest curve in the road," says Vesely of the children's album. "Who knows what we'll do next?

"Most people who listen to our music are open to different stuff, I think. We just want to see how far they'll follow us."

A "shared interest in pursuing different stuff, not having one focus that we pursue and eventually exhaust" might very well be the secret to the Rheos' longevity, he adds. "That, and the fact that we have time to do our own things."

Thus, in the lag time between albums, those desperate for Rheostatics-related material can seek out Bidini's upcoming book on the storied act of touring ("He's interviewed everybody who's ever played in a Canadian band for, like, the last 30 years," says Vesely), due in the fall.

Vesely and Tielli have also found a fun sideline for themselves scoring shows for the Discovery Channel.

"We have some recording equipment, lots of instruments and ideas," he says, "and it's a good way to put them into practice."