1. Music can be considered literature due to the fact that a lot of music uses poetry and rhyme schemes in the singing portion.
2. Literature can be defined as written or spoken material, which is very broad because there is everything from rapping to debating in literature.
3. The difference between a novel, poem, rap, song, opera, and symphony depends on the person you are asking. For example, one person might say they are all the same because they all use a form of speech, when another person might say they are different because one rhymes and the other does not.