Battle Ditty

Hi guys I have a 97 Iss Sword Muse and the other ISS in my Kartia party was a 99 Iss Sword Muse that cast a crazy skill called Battle Ditty. Im looking in the skill list for level 99 and its not listed. I asked him if it was an augumented weapon and he said no. Is there something extra required to get this skill somehow at 99 ? Just wondering why its not on the skill list. Thanks :)