Smash Bros. Brawl Music, Composers Detailed
If you look at the list, there are a LOT of composers there who aren't linked to Nintendo games. Yuzo Koshiro, of ActRaiser and Streets of Rage? Does that mean we can play as Axel Stone in the game?
Note that pretty much all the composers on the list have done a lot more work then just what is listed. Yuzo Koshiro could be in for the work he did on the 8-bit Sonic games, or Castlevania: Portrait of Ruin. But most likely it's because, as Wikipedia says, "Yuzo Koshiro arranged music from New Super Mario Bros. for the Fifth Symphonic Game Music Concert in Leipzig, Germany on August 22 2007"
Also, Akihiro Honda is clearly in to do music for Snake, so it makes sense to think at least one or two others are there to do music from one of their games.