Guest. Sorry, I didn't realise you were talking about the liturgical song at the start of the clip.

However, that is unequivocally Cinnamond singing further on. It starts at 3'40", right after the young man kisks his way through a flock of geese, or ducks or whatever they were.

And it is unequivocally Napoleon Bonaparte that he was singing. Granted the song is almost inaudible, but I turned the sound up as far as it would go, and I could distinctly make out "he was as valiant a Corsican as ever stood on Europe's land.......", as per the first verse.

BTW., Cinnamond only recorded it once and he seems to have been the only person from whom it was collected. As Pasolini used other material from The Folk Songs of Britain at other points in the soundtrack, it's hard to imagine that it could be anyone else.