Trying to categorise books that deal with the greater area of traditional music is fraught with difficulties. Some books deal with dance and it's associated music, some with dance only or the tunes only, etc. Some authors write from a perspective that includes several aspects of folk culture at once.
The answer is to have multiple links to the information from wherever it is relevant.
This page is intended to be a focal point for navigating to book categories. It is more important to get the links in than to worry about where on the page they will go. That can all be tidied up later.