can rap really be called music? why?

Rap does not even contain melody, and there is neither singing nor any instruments in most rap. I can't see that it has anything at all in common with music, aside from the fact that the record companies and rappers advertise it as such. I have no problem with different styles of music, but I can't see that rap belongs in the "music" category at all. It is just talking with some annoying data noises in the background, and contains none of the characteristics of music. Why is it considered music? Does rap even have anything in common with music at all?