Rossini is the meat-and-two-inappropriately-shaped-veg of summer opera; he’s the wag in the novelty bow tie, the two satyrs shagging enthusiastically among the lupins and lobster on the cover of this year’s Glyndebourne programme. His comic bel canto frolics are the natural soundtrack to this off-duty opera-going, a champagne-perfect combination of frothy plots and fizzing coloratura.