This article explains how to convert songs from Apple AAC digital audio format to MP3s. Only songs that are DRM-free can be converted. If a song uses Digital Rights Management protection, it cannot be converted because the conversion might remove the DRM.
Convert AAC, AIFF or Wav files to MP3 on your Mac
The first step is to make sure that the iTunes file converter function is set to create MP3 files. It can produce many types of files, including AAC, MP3 and Apple Lossless.
To enable iTunes to create MP3 files:
On a Windows PC, go to Edit > Preferences. On a Mac, go to iTunes > Preferences.
