EDNOTE. A few days ago I asked NABOKV-L for an explication of the ADA passage just below.
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 In ADA , Part I, ch. 40, Van receives a note from Percy de Prey  challenging him to a duel (arising from their tussle at Ada's 16tparagraphh birthday picnic. Van replies to the messanger:
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"No, Van did not desire to see the Count. He said so to the pretty messenger, who stood with one hand on the hip and one knee turned out like an extra, waiting for the signal to join the gambaders in the country dance after Calabro's aria."

 

MY QUESTION:  WHO IS "CALABRO"?  AN OPERA CHARACTER? THE REFERENCE TO A COUNTRY DANCE ECHOES THE SCENE (I-2) IN WHICH DEMON SEDUCES MARINA DURING A PERFORMANCE OF A PLAY BASED ON "EUGENE ONEGIN."

 
The scene has a distinctly operatic flavor and it belatedly occurred to me that Operatic basso Dmitri Nabokov is the person best qualified to comment. He graciously agreed. His thoughts follow. I add a thought of my own at the end.
 
FROM DN:
 
As for Calabro, I suspected that the initial query was aimed partly, at least, in my direction. I had already thought about it, but without specific results. Calabria, of course, is a large and somewhat backward region of Southern Italy, an inhabitant of which would be a "calabrese." Franco Calabrese was a bass who sang secondary and buffo roles at the Met. "Gambaders" does suggest a spirited country dance, a name deriving from the four-legged jumps of an energetic horse. Another sense of "gambaders" was the leather leg protection riders of such horses wore that, by extension, might have been worn during such a dance.  I have a large collection of well known and less well known Italian operas -- scores, and especially tapes made during my Monza years, mainly from frequent stage and radio performances. I would have to go through a hundred or so reels, now stored in my cellar, to be sure. But for now, the only bell this rings for me is my take on a Nabokovian fantasy: a bass-baritone bumpkin singing an aria from an invented "operina" predating Cavalleria Rusticana, but set in a similar ambience. Excuse my stream-of-consciousness  tangent. This is a Joycean year.    
 
If anything more helpful comes up, I'll let you know.
 
Best, DN
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EDITOR's AFTER THOUGHT. Mulling the thing over I wonder if the cavorting figure refers to a goat rather than a horse--since the toponym "Calabria" appears to derive from the root for "goat" whose capering is dance-like.  The country dance "Gambade" derives from the root for "Leg;" hence a jumping dance.

Also I wonder if there is a scence in Tchaikovsky's EUGENE ONEGIN in which a messenger assumes the pose VN describes (and joins in the girls dance).