iTunes question

Music tracks from most of the original illicit file sharing and download sites were encoded using the MP3 file format. The big problem from the music industry's point of view is that MP3 files are easily copied.

Most of the new legal online music stores sell tracks encoded in the WMA (Windows Media Audio) format. The notable exceptions are iTunes, which uses the AAC (Advanced Audio Coding) codec, and Sony's Connect site , which sells tracks in its proprietary ATRAC (Adaptive Transform Acoustic Coding) format.

These codecs are more efficient than MP3, resulting in better sound quality and smaller files sizes but they have one other thing in common and that is Digital Rights Management or DRM. Files downloaded from the various online music stores are embedded with DRM data that can be used to restrict how and where tracks are played and copied.

Many personal music players can play both WMA and MP3 tracks, however, Apple iPods are limited to AAC files and most Sony personal players are designed to work with ATRAC files, though most models can also play WMA tracks.

However, virtually all personal music players - including Apple and Sony models - come with software that allow users to copy or 'rip' tracks from CDs that they already own and then copy them to their players, without any restrictions.