This Mod changes the Boss Battle Themes from TBOI to Battle Music from the Pokemon Games.

-for Rebrith and Afterbirth

Instruction: (Windows only)
1.Press Start+R
2.Write "C:\Program Files (x86)\Steam\SteamApps\Common" in the Box
3.Open the "The Binding of Isaac Rebirth" Folder
4.Open "resources"
5.Put the "music" folder from the Zip Download Data
6.Finish!

Or watch a Tutorial on YouTube ;)