Jobs determined to keep iPod Apple only...........

STEVE Jobs had seven words for a subordinate when he learned that a rival company was about to introduce a program that would let music fans buy songs anywhere and play them on Apple's iPod devices.

"WE may need to change things here," Jobs said in a terse, 2005 email that was shown to jurors in federal court on the opening day of trial in a billion-dollar antitrust lawsuit that accuses Apple of using unfair tactics to maintain its dominance in the digital music business.

Attorneys for an estimated eight million consumers and iPod resellers say Jobs' email spurred an internal campaign to keep Apple's popular iPods free of music that wasn't purchased from Apple's own iTunes store.

By updating the iTunes and iPod software to block music from competing online stores, Apple maintained a closed system that discouraged consumers from buying competing music players, plaintiffs' attorney Bonny Sweeney argued.

That froze out makers of rival devices, and allowed Apple to sell iPods at inflated prices, she told jurors.

Plaintiffs' attorney Patrick Coughlin also showed jurors a 2003 email from Jobs, written about the launch of another competitor's online music store, which said, "We need to make sure that when Music Match launches ... they cannot use iPod."

Apple lawyers deny the company competed unfairly. Several high-ranking Apple executives are expected to testify during the trial.

And while Jobs died in 2011, he is a central figure in the class-action case.

Sweeney said she will show a video of Jobs testifying in a 2011 deposition later this week.

A partial transcript of that session shows Jobs asserting he couldn't remember details of actions taken several years earlier, while also betraying signs of his legendary impatience.

In one exchange with attorneys, Jobs acknowledged that he helped write a press release statement that accused RealNetworks of "adopting the tactics and ethics of a hacker to break into the iPod".

Jobs' statements have turned out to be pivotal in other antitrust cases that Apple has faced in recent years, including one in which a judge found Apple conspired with publishers to set e-book prices.

In another, a federal judge cited "compelling evidence" that Jobs was a central figure in an alleged conspiracy by leading tech companies to abstain from hiring each other's employees.

A Stanford economist will testify later in the iPod trial that Apple overcharged iPod buyers by nearly $US350 million ($A379 million).

Under USfederal antitrust law, the Cupertino, California company could be ordered to pay three times that amount if jurors agree that Apple's actions were anti-competitive.