Mark Slobin 
Folk Music [PDF ebook] 
A Very Short Introduction

This VSI offers readers something no other introduction to folk music does: a cross-cultural, comparative approach, a survey of the basic issues as they have unfolded over time, and specific examples from widely differing sites of how folk musicians themselves, as well as corporations, non-governmental organizations, and governments have made full use of the available resources, older and newer strategies, and multiple agendas that keep the folk music process alive in an increasingly interconnected, yet still localized world.