DeKALB - During a pivotal verse in "Sunken Treasure," Wilco's Jeff Tweedy held his microphone tightly in one hand and acoustic guitar in the other as if holding on for his life. In his first performance since returning from rehab for an addiction to painkillers, front man Tweedy gazed out into the crowd inside Otto's Niteclub on Wednesday and sang the line "Music is my savior." It seemed clear from the response that showered the singer that everyone in the room knew those words now carried far more meaning than before. This first of a pair of sold-out shows could mark Wilco's biggest step yet, and for Tweedy, a step toward a rejuvenated spirit. For the past two years, life had been calm for Wilco. After the band had overcome the mayhem surrounding the making and release of "Yankee Hotel Foxtrot" - when the band was dropped by its record label and longtime members Jay Bennett and Ken Coomer were voted out by the rest of the group - there was a sense that the soap opera was over. But then again, can life ever be without drama, especially in a rock band? As 2004 began, Wilco was once again faced with hurdles when Leroy Bach, a touring musician with the band since 1999's "Summerteeth," and later a full-fledged member, left Wilco after the completion of their upcoming release "A Ghost Is Born." This past April saw Tweedy check himself into rehab, followed by the cancellation of concert dates, including a noteworthy spot on the Coachella Valley Music and Arts Festival bill in California. The departure of Bach has led to the recruitment of two new members, guitarist Nels Cline and keyboardist/guitarist Pat Sansone. Mikael Jorgensen was promoted from the band's special effects team to a member. As he walked on stage, Tweedy clearly looked like a man who has weathered a storm of possibly life-threatening proportions. His hair was ragged and grown out, his body noticeably thinner. As the band's six members took their places on stage, their collective body language communicated eagerness. From the first few moments of "Ashes of American Flags," the band made no attempt to hide the reshaped dimensions of the past few months. Cline, the most skilled guitarist in the band, brought an avant-garde-minded approach, while Sansone, a partner in bassist John Stirratt's side group, the Autumn Defense, handled his new role with apparent ease. Any worries that the band would need time to jell before truly living up to the levels reached on stage in the past year were quickly wiped away. Their densely fluid wall of sound was showcased on a majority of "A Ghost Is Born." The power behind new songs such as "The Late Greats" and "At Least That's What You Said" reflected a lot of the band's added muscle and strengthened confidence. Previous material - such as "War On War" and "The Lonely One" - was given a breath of new life. In a position considered by Tweedy as the most important member of any band, drummer Glenn Kotche proved to be the fuel to the fire, bashing and stomping with the unfettered excitement of a wild animal being returned to its natural surroundings. Drops of sweat covered Tweedy's face by the end of the night, but under that sweat was a smile, one that was shared by all in the band and those in the crowd. The two-hour performance made a definite statement: Wilco is ready for the road ahead.