Tools you will need: Braindump (http://gbatemp.net/threads/braindump-prerelease-dump-game-contents-on-any-system-version.400920/) CTRtool (available in braindump thread) A RomFS builder (I suggest https://gbatemp.net/threads/release-romfs-builder.379330/) A nus3bank converter (optional, depending on your situation. I personally do not know of one, however.) An internet browser to visit brawl custom music (Google) and an SD card with somewhere around 1.2 GB of free...
[GUIDE] Smash 4 custom music with *hax 2.5
[GUIDE] Smash 4 custom music with *hax 2.5