The cause was undetermined. According to a statement posted on undertowmusic.com, the Web site of his management company, Mr. Bennett died in his sleep. Edward Burch, a friend and frequent collaborator, told The Chicago Sun-Times that an autopsy was being performed.
Last month Mr. Bennett complained on his MySpace page about severe pains in his hip. He needed hip replacement surgery, he said, but did not have proper health insurance.
Mr. Bennett, a burly figure with a cracking, plaintive rasp and a perfectionists skill in the studio, played in the Replacements-influenced power-pop band Titanic Love Affair during the 1990s, and had released four solo albums. But he is best known for his role in Wilco from 1994 to 2001. He joined after the recording of the bands first album, A.M., playing keyboards and guitar on 1996s Being There, and contributing to the bands songwriting on subsequent albums.
He took part in Mermaid Avenue, the bands 1998 project with Billy Bragg to set unpublished lyrics by Woody Guthrie to music, as well as its sequel, Mermaid Avenue II, in 2000. And on the albums Summerteeth, from 1999, and Yankee Hotel Foxtrot, released in 2002, Mr. Bennett became a key part of the bands songwriting, often functioning as a darker foil to the more fragile style of the lead singer, Jeff Tweedy.
But as documented in the 2002 film I Am Trying to Break Your Heart, about the recording of Yankee Hotel Foxtrot and the bands extended struggle with its record company, Mr. Bennett and Mr. Tweedy frequently clashed in the studio, as Mr. Bennett bristled over the bands increasingly noisy and experimental direction.
