User blog comment:Legorulez49/Why won't this work for me?/@comment-3495717-20140208224923/@comment-5192222-20140209010929

hmmm, I think I had this problem once. You can try renaming the file to something like Street_Fighter-Eagle_Stage_Music.mp3 or StreetFighter-EagleStageMusic.mp3. MUGEN acts kind of strange when spaces are involved (Why, I don't know).