Whether hunched over an acoustic guitar, a cigarette dangling from his lips, or pulsing behind a keyboard, lost in the music, Jay Bennett cut an imposing figure. During his tenure with Chicago alt-rock icons Wilco, Bennett — who died in his sleep of as-yet-undetermined causes on Saturday night at his home in Urbana, Illinois, according to his former label — often sported a ragged head of near-dreadlocked blond hair and an intense stage presence.

The singer and multi-instrumentalist was 45 and had written on his MySpace blog in April about the intense pain he still suffered from a decade-old hip injury sustained in a stage dive while playing with his previous band, Titanic Love Affair. Bennett said he was preparing to have hip-replacement surgery but was worried that his lack of health insurance might be an impediment, forcing him to sell off some of his treasured vintage recording gear.

"A decade-plus of multiple nightly stage jumps and various other rock'n'roll theatrics had finally taken a toll that I could no longer deal with," he wrote in the lengthy April 24 post explaining his absence from public view since last summer.

A native of the Chicago suburb of Rolling Meadows, Bennett finished degrees in math, political science and secondary education at the University of Illinois at Urbana-Champaign while fronting the power-pop band Titanic Love Affair between 1991 and 1996. While working in a VCR repair shop in Champaign, he got the call to become a touring member of Wilco when the Jeff Tweedy-fronted group hit the road in support of their debut, 1995's A.M. With a repertoire that ranged from guitar to mandolin and just about any kind of keyboard you could imagine, Bennett, also an accomplished singer, was a key member of Wilco during the years when then band made a shift from its initial alt-country roots to the power pop of 1996's Being There, 1999's more experimental Summerteeth and 2002's landmark Yankee Hotel Foxtrot.

It was during the difficult sessions for Foxtrot that the relationship between Bennett and band leader Tweedy soured, as Bennett attempted to gain more control over the musical direction of the band. Those struggles were painfully laid bare in the 2002 documentary about the making of that album, "I Am Trying to Break Your Heart," in which Bennett struggles against what is clearly a slow marginalization and creeping feeling that his vociferous input is not welcome anymore. In several scenes, Tweedy is shown listening with an alternately amused and confused grin on his face as Bennett discusses, in minute detail, their musical differences. "I just want you to understand me," a frustrated Bennett says, hand on forehead, early in the movie after attempting to puzzle out the tricky intro to "Heavy Metal Drummer."

"I don't have to understand you all the time, it's OK," Tweedy says with exasperation as Bennett continues to push for more clarity and the tension in the room is ratcheted up. In a band that was often intense and perhaps sometimes overly serious, Bennett's infectious, eager-to-please charm and sometimes bizarre sartorial taste brought a bit of levity to the group's performances. Though his wide range of musical contributions and songwriting skills made him a key player in the band, it was disagreement with Tweedy over the musical vision of Wilco that ultimately proved to be Bennett's undoing.

After Bennett tried to assert a wider role in the band by trying to mix and engineer Foxtrot, Tweedy fired him from the group shortly after the release of the album that would provide the band's long-sought commercial breakthrough; relations between them had reportedly remained strained in the years since. Bennett sued the band earlier this month for breach of contract, claiming he was owed royalties from Wilco albums he worked on and money from the documentary. Following his departure from the band, Bennett released five mostly under-the-radar solo albums, including his most recent, 2006's Whatever Happened I Apologize. He was reportedly working on his sixth album, tentatively titled Kicking at the Perfumed Air, at the time of his death. He also performed session work on albums by Sheryl Crow and Allison Moorer, and produced Blues Traveler's 2005 album, Bastardos! According to a report in The Chicago Tribune on Tuesday, Champaign (Illinois) County Coroner Duane Northrup said further testing is required to determine the cause of Bennett's death.

A spokesperson for Tweedy released a statement on Monday in which the bandleader said, "We are all deeply saddened by this tragedy. We will miss Jay as we remember him — as a truly unique and gifted human being and one who made welcome and significant contributions to the band's songs and evolution. Our thoughts go out to his family and friends in this very difficult time."

The homepage of Wilco's Web site features a brief tribute to Bennett as well.

[This story was originally published at 1:37 pm E.T. on 5.26.09]