Take a look at this thread on the Botsford Collection of Folk Songs. Looks like there must be two editions, three volumes each. The one that came out in the 1920's has about 100 pages per volume, and the edition from the 1950's has closer to 250 pages per volume, Volume 1 is the Americas (plus Africa and Asia in later editions). Volume 2 is Northern Europe, and Volume 3 is Southern Europe. Bookfinder.com lists it at $10-$20 per volume for the earlier edition, $25-$40 for the larger, later edition.
Is this a collection I can't live without?
-Joe Offer-