Download the following file and extract it to your home folder:
Next copy your “iTunes Music Library.xml” file to your home folder.
After ensuring that you have imported all of your iTunes tracks into Rhythmbox and that the script above has been downloaded and extracted in your Home folder you proceed to run the following command in a Terminal:
iTunesToRhythm.py -w -d ITunes\ Music\ Library.xml ~/.local/share/rhythmbox/rhythmdb.xml
For more help and further information see the iTunetoRhythm web page.