Oh yeah that’s a really old patch, you should get the most recent one from here:
The song is from Valkyrie Profile, not sure on the name.
Oh that’s just Victory Now! a track from FE7.
Which boss are you fighting against?
That will help me figure out which theme it is.
If it’s against the final bosses of the Musain route, it would be Julius’ theme from FE4.
Which boss theme?
There is Rise to the Challenge, which is from FE7, Powerful Foe, from FE8 and Tearing Shadows from FE12.