Setting Music Importing Preferences
When you add music to your iTunes library, the files are copied to your computer in the iTunes folder. Files are typically converted from their original uncompressed format to a compressed format you can choose. You can also import compressed files, including MP3s. Before you import music from a CD or copy it from another source, take a few moments to set importing preferences in iTunes.
Mac user: In iTunes, pull down the iTunes menu and choose Preferences. Windows user: In iTunes, pull down the Edit menu and choose Preferences.
Click the Advanced button.
Click the Importing tab.
Choose AAC Encoder from the Import Using drop-down menu, if it isn’t already selected. AAC is a compressed file format that’s a higher quality than MP3.
Choose High Quality from the Setting menu if you intend to import music.
Click OK to close Preferences.