To Bruce O.'s list of titles I would add, for some purposes, the journal Early Music (not to be confused with the less-useful but more-available Early Music America, a much smaller magazine).For convenience I'll expand Bruce O.s abbreviations (I hope I've got them right):
FMJ = Folk Music Journal
JEFDSS = Journal of the English Folk Dance and Song Society
JFS = Journal of Folklore Studies (?)
JAMS = Journal of the American Musicological Society
JAF = JAFL = Journal of American FolkloreT.