Just remembered a little more:

A traveler came riding by that day
And he saw the old man a-fiddling away;
Though his rooftree leaked like a waterfall,
It didn't seem to bother the old man at all.

Also,

Though the rain it fell the fiddler didn't care,
He sawed away at the popular air.


I remember thinking that air must be "popular" because people liked breathing it. I was also thoroughly mystified, at the age of seven, by the term "rooftree."

In other words, I was "stumped."