Howdy! When I was in high school, we started celebrating May Day as a school community thing, and Hal an' Tow was one of the songs we sang. The tune we sang, though, was about as different as you can get from the one in the DT... that one, I can't seem to make match the words at all. Ours was a bit faster, in a different key and had fewer notes...And the only "source" I have for our version was the school's old headmaster... he sang it for us, and we sang along, no score or sheet music provided -- just the lyrics on a xeroxed sheet (how's that for "folk process"?! ;-)).

And "our" version had an opening (perhaps a modern, "paganized") verse that went like this:

Since Man was first created
His life has been debated
And we have celebrated
The coming of the spring!

Never thought much about "Hal and Tow" -- just sort of assumed it meant "haul and tow", but now that I think about, "heel and toe" makes more sense.

On our lyric sheets, "jolly rumbalo" was written as "Jolly rumble-o", and I always took it to mean that those singing guys were celebrating the 'jolly rumble' they've just come back from in the forest... ;-)