Song

I was working on a poem yesterday and it has become a song in my head. This raises a question on what is the difference between the two. Poems have had musical accompaniment in many parts of the world: Africa, Joseon-Korea, Shakespeare's plays, etc. My argument is that other than the physical sound compared to the mental tune there is no difference. If I play music or write poetry and have someone else read it, I am doing the exact same thing.
This matters because songs have been seen as crass or part of the underclasses' entertainment while the upper-class enjoyed more "intellectual" activities like poetry. If what stimulates the different groups is really the same it also shows that the social classes are not so different. If groups are the same it turns the idea of one class versus another on it's head. Perhaps I am getting carried away though. Tell me your thoughts.