Apple has been working with musical artists and their sound engineers to offer up the highest encoding practices possible for submissions to the iTunes Store, and has now begun to showcase some of that work, launching a new "Mastered for iTunes" section on the iTunes Store.
Apple currently makes use of the Advanced Audio Coding (AAC) codec for music compression and while, to the average listener, these files may sound great, to audiophiles, sound-engineers and the artists who create the music, they're not getting the full array of sound that they intended for you to hear. Most recently, the likes of Neil Young, Dr. Dre and even Jimmy Iovine, head of Interscope-Geffen-A&M have all gone on record as not being in favor of the sound quality listeners are getting when purchasing music. The Advanced Audio Coding (AAC) codec used by Apple and various other digital media service providers, causes quality loss during the conversion from the 24-bit 192kHz original recording. By the time consumers actually get the file, you're only receiving as little as three percent of the original 192kHz quality.
With the launch of the Mastered for iTunes section, Apple is now transitioning from their original methods of taking the CD masters and encoding them to the 256kbps iTunes Plus files, and is instead asking publishers to submit the full high-resolution 24-bit/96kHz files so they may be the base file for encoding. To help with the transition for music publishers, they've also released a white paper documenting the changes and advising how to go about the process of submissions as well as providing new mastering tools to go along with it.
In the end, the ultimate goal here is to have everyone obtaining the highest quality audio files as possible from the iTunes Store. Neil Young noted previously that he had been working with Apple on this change prior to the death of Steve Jobs and since then, there hasn't been much word from Apple. Now, with the roll out of the new encoding standards and the Mastered for iTunes section, we know why Neil hasn't heard any word from Apple. They were busy making it all happen behind the scenes.