Apple CEO Steve Jobs has been ordered by US Magistrate Judge Howard R. Lloyd in San Jose, California to answer questions in an antitrust lawsuit that alleges Apple of music-downloading monopoly.

The judge favoured a complaint filed by lawyers for consumers and gave permission to conduct limited questioning of Jobs on changes Apple made to its software in October 2004 that prevented digital music files by RealNetworks from being operable with its iPod music player.

However, the judge rejected requests to allow broader questioning of Jobs about other related issues.

The current dispute is about a software called Fairplay that allowed only music bought on iTunes to be played on the iPod.

The complaint says that the software resulted in a music-downloading monopoly for Apple with its iPod player and iTunes store.

Real has denied any involvement in the class-action lawsuit.

In support of the ruling, the judge said Jobs had unique knowledge about the dispute.

Lloyd said, "The court finds that Jobs has unique, non-repetitive, firsthand knowledge about the issues at the center of the dispute over RealNetworks software."

Apple may appeal the decision, but has not commented on the matter so far.

Jobs took a medical leave from the company starting January 17, but made a rare appearance for the launch of Apple’s iPad2 earlier this month.