Thank you all very much.

@Nigel Parsons: that line in "The Man Who Owned Broadway" might indeed be a memory of o allusion to the actual song (though envious kings could indeed be independently engendered).

@Guset.Grishka: There is a deep pleasure in finding "lost" thnigs from one's childhood. Interesting how "high culture" can become something else over the years (from opera to infantschool song: though not learnt tere byme). And extra information of the sort one would never dream of finding, the worldwideweb notwithstanding, gives rise to "the experience of grace", or something like it.   

I apologise for not being able to distinguish between the Rossini Italian of the first son in "The Double Clue" from the French of "Chanson d'Estelle" by Benjamin Godard, words by Jean-Pierre Claris de Florian, from a "pastoral play", "Estelle et Némorin", alternative form btsa in Occitan, closer to Italian, where Estelle inquires about her shepherd lover.

I do not remember whether the fictive speaker was female or male, an Estelle or a mistaken Florian, but it matters not.   

I am grateful for the YouTube French and English singing, and for the sheet music, and the powertray appended...

Sanjay Sircar