I read an article on Mathers the other day and the lyric they quoted for my admiration had him rhyming "Math" with "Half".

That looks weird in print, but maybe it might not be so weird when spoken aloud. Math does rhyme with Half in some accents, with "Th" becoming "F", and a short "a" in Half, so that it would be Maff and Haff. Of course, whether the guy in question uses that kind of pronunciation I don't know. I've never got into listening to rap much myself.

One of the types of music in which rap is rooted, and which has developed alongside it (in a much more interesting and less commercially degraded way) is Dub, coming from Jamaica (and with roots in American music - this kind of pl;process goes round in circles). Here is a site with some interesting sound files; and here is a site with an essay about this type of music, and a massive bibliography and some good links.

As has been said, if you judged folk music by some of the stuff that gets the most media coverage, you'd be badly misjudging it.