When asking "How much folk music is there?" you have to keep in mind that every language has a culture associated with it, that means the more than 6,000 languages in the world each of must have a body of traditional songs and stories--

The next thing to keep in mind is that only around two thousand languages have a written form, so the songs and stories are only orally transmitted, and there is no way to transcribe them.

The last thing is that more than a quarter of the languages each have a thousand speakers or less and are dying--It is estimated that nearly 3,000 languages will be extinct within a hundred years.