Sometimes one senses that more people have heard of Wilco than have actually heard the Chicago-based band.

"We exist very humbly," says bassist John Stirrat, who has stood alongside Wilco's resident-genius Jeff Tweedy for well over a decade, beginning with the dying days of alt.country darlings Uncle Tupelo. "We are not about rock star excess ... unfortunately."

Well, Tweedy was responsible for Wilco's bizarre jump from the alternative press to the tabloids earlier this year, when he sought treatment for an addiction to painkillers.

"There was a problem with visibility," understates Stirrat. "Suddenly we were on CNN; it was weird. But media is such a business. And it's a testament to the band that it didn't faze us."

But then Wilco has never been about what people think they're about anyway. That became evident shortly after the country-rock album Being There when Tweedy's musical vision for Wilco became increasingly adventurous -- even as the band explored their folk roots by recording collections of Woody Guthrie material with Billy Bragg.

The latest Wilco release, A Ghost Is Born, finds the band on its most solid ground to date, as a critical and commercial success. (Tonight's Capital Music Hall show sold out weeks ago.)

It's a step up from its predecessor Yankee Hotel Foxtrot's wild ride -- one which began with rejection by Warner Music and resulted in the band's bestselling CD and a celebrated documentary.

"There's no way we'd want to gloat about it," Stirrat diplomatically says of the YHF experience (the album, like A Ghost Is Born, was ultimately distributed by Warner). "It was a simple situation: They didn't feel they could sell it. But they were nice enough to sell it back to us, which they didn't have to do."

Spoken like a trouper. Which Stirrat surely is, given his loyalty to the ever-changing band and to the sometimes temperamental (please refer to the documentary) Tweedy.

"There have been difficult times," Stirrat concedes, "and Jeff can be very demanding -- on himself as much as anyone else. But it's all just phases. This is a rock 'n' roll band that's been around for over 10 years. That's a lifetime these days."