If I may be correct to say so myself, isn't Kefka the final boss? I don't recall the battle having that music.
EDIT: Never mind, didn't listen to the entire thing. Was thrown off by how fucking LONG it is.
Kimi wa ne tashika ni ano toki watashi no soba ni ita
Itsudatte itsudatte itsudatte
Sugu yoko de waratteita
Nakushitemo torimodosu kimi wo
I will never leave you