The reason that music has static or a new song randomly plays is because you have overwrote on an old brstm and they have fused together. Best thing to do is to make sure the song you are putting in the folder is not already in the folder (eg: A01.BRSTM is already in the folder so you can't put another A01.BRSTM in that same folder.) Delete the old one and put your new song in the folder. Just do not overwrite the songs or you'll technically be fusing them together (in brawl hack retrospective)
This is not true cause of a few things.
1. The files get overwritten not fused.
2. I overwrite every single song i have every time and i have yet had this nor have i ever met someone who had this.
3. Overwriting a file is just saying: i remove this bit and place this bit and that for every bit. So it's not fused in any way.