Some industry observers have cautioned against taking on Mr. Jobs directly. “When your customers are iPod addicts, who are you striking back against?,” said Ken Hertz, an entertainment lawyer who represents artists like Beyoncé and the Black Eyed Peas. “The record companies now have to figure out how to stimulate competition without alienating Steve Jobs, and they need to do that while Steve Jobs still has an incentive to keep them at the table.”

But other music industry executives say the major labels must take a harder line with Apple at some point if they are to recalibrate the relationship. In particular, they say, it is unfair for Mr. Jobs to exert tight control over prices and other terms while profiting from the iPod. Mr. Jobs, in February, noted that less than 3 percent of the music on the average iPod was bought from iTunes, leading music executives to speculate that the devices in many instances are used to store pirated songs. (Of course, users can also fill their players with songs copied from their own CD collections.)

Apple has now sold more than 100 million iPods, and the device’s ties to iTunes have helped make Apple the leading seller of digital music by a wide margin. The iTunes service accounts for 76 percent of digital music sales, and the contract talks come as it is on the rise — Apple recently surpassed Amazon.com to become the third-biggest seller of music over all, behind Wal-Mart and Best Buy, according to data from the market research firm NPD.

All of that has transformed Apple into a prominent gatekeeper, wielding influence as a tastemaker by highlighting selected artists on iTunes storefront, and as an architect of the underlying business dynamics.

Apple has stuck to a pricing system that charges a flat 99 cents for a song since iTunes started four years ago (except for the recent introduction of songs without copy protection, which carry a higher price). Mr. Jobs has long argued that a uniform system and low prices will invite new consumers and reduce piracy.

But some music executives have been chafing at the flat rate that Apple has insisted upon in its contracts with the big record labels, and they have been pressing publicly or privately for the right to charge Apple more for popular songs to capitalize on demand or, in the event of special promotions, to charge less. Edgar Bronfman Jr., the chairman of Warner Music Group, reinforced that idea at a recent investor conference, saying “we believe that not every song, not every artist, not every album, is created equal.”

In the backdrop of the pricing dispute is an investigation by European regulators who are studying the roles of the music companies and Apple in setting prices in certain international markets.