I've got side two of LZ III on now. As Steve L. mentioned earlier, its mainly acoustic blues/whatever (though no one would confuse the banjo on Gallow's Pole for Pete Seegar). As well as "Gallows Pole" there's some really nice slide work on "Hats off to you (Roy) Harper". Unfortunatly, the cassette I've got doesn't give any credits at all, not even "traditional", let alone someone specific.

I did go back to my Leadbelly book to look for more information about Gallows Pole. The book I've got (an Oak Publications book about the 12-string, from the early 1970s) credits the song as an "old English ballad", which probably qualifies as "traditional" if correct.