An opera primer: Glimmerglass regular explains the basics of the genre By ROBERT MOYNIHAN • Special to www.AllOTSEGO.com First, opera is supposed to be quite serious. One writer of praise for Verdi’s “Trovatore” observed, totally without irony: “When the soprano part is sung as Madam X sings it, one cannot survive without tears.” As for the composer himself: “He made a nest for singers in his music like the mother-bird warming her young.” Such comments have as much relation to…