I did not understand when mentioning the first contest that it was to make a Rap/Hip Hop song instrumental for the AutoRap app. I thought it was meant that a person was supposed to use the AutoRap app for rapping which is less interesting in my book.
In either case as an instrumental it makes sense for a Rap producer to participate as it will give a decent amount of exposure.
To read more:
http://smule.openlabs.com/