Hello,
I dont mean to be negative.
but I think that is a very weak area to base an essay around,
I dont think it would be impossible to write a decent interesting essay,
but the link between racism & rap music is really an oddball idea that many people would feel does not exist at all.
I think there could be some interesting things to research in that area, such as the use of extremely visceral violent, racist, criminal, sexist/sexual, anti-gay etc - lyrics becoming completley socially acceptable through popular "black" corporate music (rap)
For example if a white group made music about murdering , robbing & raping - I dont think it would be that well received!
You could research the evolution of early hip-hop to "gangsta-rap" and the evolution of "gangsta-rap" to the hugeley corporate world of american popular music in the mid 90's to present. where "black" or rap music is the number one form of popular chart topping music in america.
You could try and research attitudes in white smalltown america toward NY/LA rooted "black" music which is almost always graphically sexual/criminal or violent.
you could see if some people frown upon this, and find prejudices against black people through it.
Like I said, you have a lot of hard work ahead of you if you choose that route.
Maybe you could choose something easier such as rap music = gun crime?