[mindonstrike]

After making your changes manually in the database, In edit songs, Use the asterisk to bring up every song and then highlight all of them to select every song in the database (in multiple mode) and click apply.

Caution: You run the risk of screwing up your genres, language and mpx settings. There were some 4.x versions that were effected. I would do some small scale experiments to make sure there are no unintended consequences.