Tried letsdump on the Wii Play brsars and it generates a RWSD file OK, but vgmstream can't seem to play it. Is the file not being dumped correctly, or is it that vgmstream cannot play the files?
letsdump is really dumb. It pretty much just dumps the entire contents of the brsar as one big chunk. For situations where the entire contents of the brsar is a single RWSD, this works, but it isn't all that common. The Wii Play brsars are a bit more complicated than that. It would take a brsar_unpack that doesn't suck to get at their BGM.