I think Music can be considered music. If you think about it, they're pretty similar to each other. The difference between a novel/poem and a rap or a song is that the rap is in a music form. The only difference I see is that one has tone/noise/sound to it and the other doesn't. Most songs usually have a story behind the sound. If you actually read the lyrics instead just listening to the music, you'll see that the song is a story. So music can be considered Literature.