Monique, don't misunderstand, the Berthier volumes are an excellent resource for French songs, folk or other, but the indexes are difficult to use for one who is used to a different usage of terms.
I am considering copying the indexes, cut and paste, to see if I can make an alphabetical listing. (if I get the time!)

Treatment of articles doesn't seem to be consistent.

To continue this digression, which really doesn't belong here:
Seeing Stephen Foster's "Old Black Joe" listed as a folk song grates; Foster was one of the great U.S. song composers, and the song was spread by reams of sheet music and latterly many recordings.

"Moby Dick" seems to be by a modern French composer; your explanation that titles in caps are not in the volume explains why it couldn't be found. Certainly not a folk song in English usage.