It's the song that plays during the prologue chapters in FE12. It does sound similar to the prep screens in the GBA games, but it isn't the same song.
I'm going to copy a reddit post I made about music since it was a decently long post and explained my love of FE music.
As a big game music nerd, I have a massive list, but I'll boil ti down to a few. If a character has a theme in the Tellius games, it usually fits their character perfectly, giving a certain "tone" to their dialogue. Radiant Dawn did an amazing job of delivering emotion and tone to scenes, which is one of my reasons for loving the game and its story. Good examples of this are:
Skrimir's Pride. If this song plays, Skrimir is probably doing something stupid or being a total badass. Sometimes both. But it helps define his base nature, how he knows only the tribalistic ways of Gallia until he leads his army in a war that isn't how he expected a war was supposed to be fought.
Zelgius the Brave. This song speaks volumes about Zelgius' character and the situations that it's played. It's a blaring, sounds-of-war style BGM, which overwhelms you whenever it's played. It's intimidating but in the opposite way to Skrimir's Pride, because it sounds much more refined and calculated.
Child of Chaos. This song is my favorite in the series, mainly because it punctuated the theme of FE10's Part 4 perfectly. After the massive war that threatened to destroy the continent, the threat of the Medallion that had been ignored was put at center stage, and what everyone they knew about the nature of chaos was wrong. Yune wasn't evil incarnate, she was the spirit of freedom, good and bad. The calming and slightly whimsical nature of the song made Yune a sympathetic character and made her stories seem sincere. Emotional overload.
![[face_tongue]](https://cdn.statically.io/img/www.ignboards.com/styles/ign/ign/smilies/classic/stickouttongue.gif "Stick Out Tongue [face_tongue]")