I should put in my own comment here, in response to Nick Dow's, to make sure I haven't given a false impression.

Romancing the Ballad isn't exactly about the ballad "King Orfeo." Its real purpose is to examine the relationship between ballads and medieval romances. There are a number of instances where a ballad tells a tale found earlier in a romance -- so "King Orfeo" tells the story of "Sir Orfeo." But, also, "Hind Horn" (Child #17) tells a version of an incident at the end of the very oldest Middle English romance, "King Horn." "Blancheflour and Jellyflorice" (Child 300) is a sort of version of the romance "Floris and Blanchefleur." "The Marriage of Sir Gawain" (Child 31) is "The Marriage of Sir Gawain and Dame Ragnall." (In that particular case, it hasn't even been shortened all that much.) There are others.

That the ballads and romances are related is not generally questioned, at least in the four cases I've cited. (There are more dubious cases.) But which is the original? Were the ballads expanded to make the romances, or were the plots of the romances cut down to make the ballads?

Typically the assumption has been that the romances are older, because the earliest copies of the romances are older. Usually much older -- e.g. the most significant copy of the romance of "Sir Orfeo" is usually dated to the fourteenth century (sometimes to c. 1330), whereas the earliest copy of "King Orfeo" is nineteenth century. But there were a few people who argued the other way, and no one offered actual proof.

I set out to supply that proof in Romancing the Ballad. I used the Orfeo pair because (a) "Sir Orfeo" is a really good romance, (b) it allowed the most definitive conclusion, and (c) the surviving copies of "King Horn" (the other case probably most susceptible to proof) are so messed up that scholars can't even agree on whether it's supposed to have two or three stresses per line!

To do this analysis, I had to try to produce the fullest possible version of "King Orfeo," to allow maximal comparison. So Romancing the Ballad involves a textual reconstruction, not properly a comparison.

It did allow quite unequivocal proof, in this case: the ballad not the original; it is derived from a romance, either "Sir Orfeo" or the fragmentary "King Orphius."

OK, you can all go back to actual music now. :-)