Hmm the other thing is that there are at least a couple of Mason's Apron variants... I'm not a fiddler, but in Scotland the tune (I think - stand to be corrected tho').. is played so that it's usually a 2- part tune, but the Irish version has 3 or maybe 4 parts...

I think that in any case, the famous fiddler would have done well to explain what he was trying to demonstrate....

Cheers, Steven