RnB influence

Rhythm and Blues started out in the black community in the 50's and it was appriciate by most white people. Not only appriciate, many white musicans were influenced by the music as well, even foreigners. In Cadillac Records we touch basis on this. Leonard Chase started out with producing RnB, and then Rock and Roll. I find it interesting that RnB music has also slown down since. Is there a difference between the RnB music from the 50's and the RnB music today or the 90's? And if so, has the audience of RnB changed? Do you think that the evolution of Rock and Roll played a part in this?