Downloaded music can now come in many forms, with Audiophile HD downloads available in PCM or FLAC format, whilst mainstream distributors still sell mainly MP3 or AAC files. Most of us are familiar with the term MP3 but you may not be aware that if you buy music from the iTunes store it comes to you in a similar although arguably superior format called AAC (standing for Advanced Audio Coding and denoted by the file extension .m4a)
Mastered For iTunes is in effect a new standard for digital releases in the AAC format, which seeks to get the best possible results out of Apple’s AAC encoding processes by using the highest available resolution in the master, whilst avoiding certain extremes which could produce undesirable side-effects in the encoded file.
Whilst you can put anything into a WAV file for download, an MFiT master has been checked and if necessary modified to ensure it meets Apple’s specifications as regards inter-sample clipping and sound quality.
Should you wish to have your music available in this format, to be sold in the iTunes store in the Mastered For iTunes section, you should ideally record and mix your project at 96 kHz and when you book your mastering session let me know that you want an MFiT master.