By AppleInsider Staff

Published: 03:00 PM EST

An Apple firmware update has disrupted Real's Harmony.

Apple Computer has quietly updated its iPod software so that songs purchased from RealNetworks' online music store will no longer play on some of the Mac maker's popular MP3 players, CNet News.com is reporting. The move could render tunes purchased by many iPod owners unplayable on their music players.

In March of this year, RealNetworks CEO Rob Glaser used several avenues to exhort Apple to open up the iPod to additional file formats. Each request was successively denied.

To combat Apple's unfavorable response, Real in July announced its Harmony technology, which lets users play music bought and downloaded from its online music store on the iPod. To create Harmony, Real created a way to translate songs downloaded from Real's store from Real's Helix DRM scheme to an equivalent of Apple's FairPlay when loaded onto an iPod.

Apple immediately responded to the announcement of Harmony in a public statement, claiming that Real "adopted the tactics and ethics of a hacker to break into the iPod."

In this initial effort to block Harmony, Apple reportedly made changes to the iPod's firmware, which is the low-level software that powers consumer electronics such as MP3 players and cellphones. The changes apparently came in an update to the iPod software released by the company in mid-November.