Any ideas on this
 

There is a rap/dance song that has been around a couple years that goes great with an adult site of mine. I want to run it in the background on my index page. How would I go about getting permission to use it ? The artist? The record company? Or can I use a snippet of it????

Just go ahead and use it, when you get sued, it's free publicity.
Make sure surfers aren't able to turn it off or down, either, they love that!