Open iTunes and select iTunes Preferences on a Mac, or click "Edit," and then "Preferences" on a PC.
Choose "Import Settings," and select "MP3 Encoder" in the "Import Using" menu. This will dictate which format iTunes converts music files to. Click "OK" to exit out of "Import Settings" and "OK" again to exit out of iTunes Preferences.
Click on the music file in your iTunes library that you would like to make smaller.
Right-click the file and choose "Create MP3 Version." A MP3 version of the file will then appear directly above or below the original file (depending on how the list is ordered). The MP3 version of the file will be compressed. Typically, MP3 files are one tenth the size of a normal CD audio file.
Open Switch and click "Add Files." Select the music file you would like to make smaller.
Choose the ".mp3" format from the "Output Format" menu.
Click "Browse" located next to "Output Folder" and select where you would like to save the smaller version of the music file.
Click "Convert" and the music file will be saved in a smaller, compressed MP3 format.
Open dBpoweramp. Click "Browse" and select the music file you would like to make smaller. Then click "Open."
Select "MP3" from the "Converting To" menu.
Click "Folder" next to "Output Location" and select where you would like to save this smaller version of the music file.
Click "Convert" and the music file will be saved in MP3 format.