Well, I actually found a way to mod special attacks, and they don't disappear after the character levels up, and it won't crash the game too. I've also found a way to mod party members, I've tested it and it worked, however I need more time to find the correct values of every characters. At this point I haven't found anything about adding Crescendo or Serenade to the party but I'll keep looking for it, though I think there's no way to do that. Now I could use some help from a developer to help me creating a save editor. I know the game is very old but is very cool and I bet lots of people would like to play it again with a SE to make it better.