Although Apple's proprietary M4P file type delivers high-quality sound, the format is not supported by other digital music devices aside from Apple's iOS devices, making the purchased content useless without specific media players. There are a number of third-party applications available to purchase for converting MP4s, but the simplest method is to use iTunes' importing encoder to convert MP4s to MP3 from a blank CD-RW. The method is free and doesn't require you to download any third-party applications.
Launch iTunes on your computer and insert a blank CD into your disc drive.
Click the "+" symbol below the left side bar to create a new playlist and name it "Convert to MP3."
Drag and drop the M4P files from your iTunes library to the "Convert to MP3" folder and click the playlist.
Click "File" in the menu bar of the application window and select "Burn Playlist to Disc." Eject the disc when iTunes has finished burning the playlist.
Click "Options" in the menu bar of the iTunes application window and select "Preferences."
Select the "General" tab and click "Import Settings." Click the drop-down menu and select "MP3 Encoder."
Insert the burned disc in your disc drive. Click "Yes" to import the songs to your library. The songs are then added to your iTunes library as MP3 files.
The converted tracks will appear as duplicates in your media library.