I've been up to my neck in opera. Last week started with an all-Verdi concert of the One World Symphony at Holy Apostles (with a sing-along of the chorus of the Hebrew slaves from "Nabucco" - what fun!), picked up speed with Les Arts Florissants' altogether splendid "Atys" on Tuesday and then went as fast as those neutrinos at CERN to attend a pre-preview of Nico Muhly's not yet opened new opera about Fundamentalist Mormons, "Dark Sisters," on Friday. I thought that was it for a while. (Next week's a biggie again, with the Met's "Barber of Seville" and a modernist-postmodernist "Three Penny Opera" at BAM.) But a friend picked up an extra ticket for the free outdoor simulcast of today's Met Gala Season Opener, Donizetti's "Anna Bolena," with Anna Netrebko and a stellar cast: how could I say no?