Rolling through New York City in the back seat of his black Maybach, Jay-Z touches a button to let more light through the translucent roof, then tugs back a window curtain to peek out at the rainy streets of his hometown. The rapper went from a Brooklyn housing project to a top corner office near Times Square, a path traced in "Empire State of Mind," his anthem to the city that has taken a place next to Sinatra's.

At age 40 and still rapping, Jay-Z inhabits the rare zone where cultural cachet and corporate power meet. He's had partnerships with Hewlett-Packard, Coca-Cola, Budweiser, Reebok and Microsoft. Forbes magazine put him on the cover of its current 400 "Richest People in America" issue, even though at $450 million he was only "on his way" to cracking the list ($1 billion was required this year). He's posted more No. 1 albums on the Billboard 200 list than anybody but the Beatles, has won 10 Grammy awards and sold 45 million albums.

He's using his clout to rewrite some industry rules. His music company hedges the unpredictable business of music sales against steadier revenues from music publishing, artist management and touring. The company, Roc Nation, was created out of a $150 million, 10-year, profit-sharing deal with concert giant Live Nation, which has made bets on acts such as U2 and Madonna that are similar, though narrower in scope.

Jay-Z's ventures include an ownership stake in the New Jersey Nets; a sports-bar chain called the 40/40 Club and a Greenwich Village bistro, the Spotted Pig; creative and operational control of the Rocawear clothing line that he sold in 2007 for $204 million; and the Carol's Daughter beauty line he co-owns.