I did not try to convert music so I don't know but, I think tools should be better now to use as they get updated over the time. So you can try it again, maybe there are also other tools usable for this.
What about the brsar file patcher and a tool to create brstm files (not the brawl one, use a general brstmconverter) together? That should work I think.
Well, but, I don't really know what does work or not or I would have to try it myself, but I don't have the time. I can only do testing, if there is any new content out here. If you get the music working than I would have something new to try out.