When you say extract background music, what do you mean?

Do you want to remove the background music or remove the vocals?

Unfortunately, neither one can be done easily or completely. Although, depending on how it is to be used, it is possible to some extent.

You may want to read this similar posting:

http://www.magix.info/us/how-to-erase-the-vocals-from-an-existed-song.knowledge.39545.html