The second mainstay opera of SFO’s season to feature equally strong alternating casts, this Tosca, thanks to the company’s shrewd General Director David Gockley, gives us the dueling divas Angela Gheorghiu and Patricia Racette. Very different singers, but equally strong in the histrionic department, they respectively fret, fight, and kill for Massimo Giordano (making his SFO debut) and third-year Adler Fellow Brian Jagde (making a major career move). Stabbed in the process are the Scarpias of Roberto Frontali and Mark Delavan (who has great rapport with Racette). Those who attend both performances are free to sport the Opera Queen Medal of Honor.