[Perdition]

Either an asago or patrion item that when used, you can upload a music file within the normal size limit and define a skill/spell similar to how you can in battle quotes. Upon using that skill/spell in combat, the battle music would change to what the uploaded file is. Perhaps you can even specify the music to trigger in specific scenarios like how you can for battle quotes (IE, the turn on Eclair, Graft only when Mass is used, etc.)