Well, if you want to sing it slowly (and REALLY drag it out a long time), if fits THE ROCKS OF BAWN.
A little more upbeat, you could sing it to BRENNAN ON THE MOOR, repeating the end of each verse (And the name of this young troubadour is Heroprotagonist, Heroprtagaonist, and the name of this young troubadour is Heroprotagonist).
You could also use ROSIN THE BEAU, but the syllables don't fit quite as well as BRENNAN ON THE MOOR. (Heroprotagon-iiii-ist, oh Heroprotagonist, and the name of this young troubadour is Heroprotaaaaagonist.)
FUN SONG!
Alice