Creative Technology has joined the list of companies which own patents that could be infringed by Apple's popular iPod music player.

Such patents could force Apple to pay licence fees and make it either raise prices or sacrifice profit margins.

Creative makes the Zen and Nomad Jukebox portable music players. The company was awarded a patent earlier this month for a technology that "automatically files tracks according to hierarchical structure of categories to organise tracks in a logical order", according to a document filed with the US Patent and Trademark Office. 

"We developed a way for a user to efficiently and intuitively navigate and select tracks from a significant number of tracks stored on a player," said Creative chief executive Sim Wong Hoo.

"Before this invention, there was no intuitive and efficient way to deal with the large number of tracks that could be stored on a high-capacity player."

In a press release issued earlier this week, Creative accused Apple of infringing on the patent with its iPod and iPod Mini players. The company has not filed any legal claims against Apple.

Creative was one of the first vendors to create and sell a portable digital media player, and started shipping the first product covered by the recently awarded patent in September 2000. Apple only introduced the iPod in October 2001.

Apple has filed a patent application for the iPod user interface, but it was rejected two months ago.

Reports emerged last month that Microsoft had been awarded a patent on the generation of digital playlists and the building of music libraries.

However, David Kaefer, director of business development at Microsoft, has stated that he doubted whether this patent applied to the iPod.

The Microsoft patent is more about the player learning what kind of music the owner likes in order to deliver similar content, and less about how a user navigates through the music collection.