For future reference, I'd not bother with this one: he failed to explain two of the roots of the carol in celebration and in the rondelli, the monastic round dances tracing the continental labyrinths found in so many churches. True, he mentions the later degeneration into ring-dances, but suggests there is a pagan origin to them, which is nowhere documented in anything other than some of the symbology in the words, often of folk origins and much later. A stronger case can be made - and he did not - that they may be derivative from dances in the Orthodox Church derived from Jewish tradition.
In his discussion of the death of West Quire music, he presumes everyone knows all about the Oxford Movement and fails to mention the chief medium of its impact, placing organs in the Quire gallery, happily playing later organ arrangements of earlier quire melodies. A superficial mess, in other words.