Andrew, a question. At what point does an ensemble become a chorus? Cosė had the smallest chorus I've ever seen in an opera. I didn't count them, but there couldn't have been more than 10 or 12. It was a delightful performance...I think I enjoyed Cosė more than anything else this season.

Incidentally, I found this in Wiki:
According to William Mann,[6] Mozart disliked prima donna Adriana Ferrarese del Bene, da Ponte's arrogant mistress for whom the role of Fiordiligi had been created. Knowing her idiosyncratic tendency to drop her chin on low notes and throw back her head on high ones, Mozart filled her showpiece aria "Come scoglio" with constant leaps from low to high and high to low in order to make Ferrarese's head "bob like a chicken" onstage.[7]