His insecurity on this point reflects the trepidation that is consuming the music business. Seemingly overnight, the entire industry is collapsing. Sales figures on top-selling CDs are about 30 percent lower than they were a year ago, and the usual remedies aren't available. Since radio is no longer a place to push a single, record companies have turned to television and movies. "High School Musical," which originated with a Disney Channel television show, was the top-selling album of 2006, and not only has "American Idol," with its 30-million-plus audience, created best-selling singers like Kelly Clarkson and Chris Daughtry, but an appearance on the show can also boost sales. When Jennifer Lopez performed on "American Idol," it was considered worth noting that her album "Como Ama Una Mujer," already out for four weeks, dipped only 7 percent rather than falling by the usual double digits. More impressively, songs that are heard on popular shows like "Grey's Anatomy" become instantly desirable. When the Columbia artist Brandi Carlile's song "The Story" was featured on the ABC show, it posted a 15 percent jump in sales and was downloaded 19,000 times in one week. Before being heard on the show, the song had been available for nearly two months without any notable interest.

"Until very recently," Rubin told me over lunch at Hugo's, a health-conscious restaurant in Hollywood, "there were a handful of channels in the music business that the gatekeepers controlled. They were radio, Tower Records, MTV, certain mainstream press like Rolling Stone. That's how people found out about new things. Every record company in the industry was built to work that model. There was a time when if you had something that wasn't so good, through muscle and lack of other choices, you could push that not very good product through those channels. And that's how the music business functioned for 50 years. Well, the world has changed. And the industry has not."

Steve Barnett, who is 55 and was the sole head of Columbia until he agreed to split his role with Rubin, was president of Epic Records, also a division of Sony, until 2005 and was well aware of the seismic shifts in the business. Barnett's corner office on the 25th floor of the Sony building is like a miniversion of the Hard Rock Cafe — autographed guitars belonging to Jeff Beck, Korn and Angus Young from AC/DC rest in their stands, and the walls are covered with vintage posters from the celebrated New York rock venue the Fillmore East. To the right of Barnett's large desk, above the framed Johnny Cash portrait, is a sign that reads, "Your Faith Needs to Be Greater Than Your Fear." "I have always believed that," Barnett told me in mid-August, "but it seems particularly relevant at the moment."

Barnett, who is English, is a sharp counterpoint to Rubin. He lives with his wife and two of their four sons in Connecticut. He has neatly parted sandy brown hair, and on the day we met, he was dressed in a blue button-down shirt, tan slacks and Gucci loafers with dark socks. Barnett is polite, careful, aware of his corporate status. Yet he supported recruiting Rubin. "My wife's father is Dick Vermeil, the former coach of the St. Louis Rams," Barnett explained. "My sons would go to training camp, and when Marshall Faulk started playing for the team, they called me and said, 'Not only is this guy a great player, he makes everyone around him better.' Of course, the Rams went on to win the Super Bowl. I think Rick Rubin is our Marshall Faulk. I knew he would change the culture here."

By the time Barnett first approached Rubin about coming to Columbia, Rubin had already decided that he would have nothing more to do with Columbia Records. This was because of the company's handling of the Rubin-produced Neil Diamond record "12 Songs" in 2005. Diamond was a hero of Rubin's, and he spent two years working on the album, persuading Diamond to record acoustically, something he hadn't done since the '60s.

"The CD debuted at No. 4," Rubin told me at Hugo's, still sounding upset. "It was the highest debut of Neil's career, off to a great start. But Columbia — it was some kind of corporate thing — had put spyware on the CD. That kept people from copying it, but it also somehow recorded information about whoever bought the record. The spyware became public knowledge, and people freaked out. There were some lawsuits filed, and the CD was recalled by Columbia. Literally pulled from stores. We came out on a Tuesday, by the following week the CD was not available. Columbia released it again in a month, but we never recovered. Neil was furious, and I vowed never to make another album with Columbia."

But when Barnett flew out to Los Angeles to discuss the job with Rubin, Rubin was intrigued. "I felt like I could be a force for good," he explained. "In the past, I've tried to protect artists from the label, and now my job would also be to protect the label from itself. So many of the decisions at these companies are not about the music. They are shortsighted and desperate. For so long, the record industry had control. But now that monopoly has ended, they don't know what to do. I thought it would be an interesting challenge."