Before I post my findings I think in view of the combative nature of this thread I ought to point out a few realities highlighted by McCarthy.
Despite Motherwell's name appearing on the cover of Minstrelsy Ancient and Modern he was not directly responsible for about half of the items it contained as these were edited by SOE before he took over. I have worked out that the whole was originally published in 12 perhaps 13 parts and that M didn't take over the editorship until about the end of the 6th part although before that he contributed advice and notes no doubt. (I've not managed to find out who the original editor was but it should be easy enough to do so.)