Adding Creative Commons license tags in MP3, Ogg, and other audio files, so that when you run Rhythmbox or your favorite music player, you could easily look up the license e.g. BY-SA etc. for your CC music, while at the same time it could display "Copyright NameOfRecordCompany" for non-CC e.g. copyrighted music.
Through this, if you regularly play music in public or use music in commercial projects, you could easily filter which music you can legally use.