Of course, the opera requires two sopranos who can bring distinctive qualities to the roles and match each other with vocal and dramatic prowess. KO executive director Brian Salesky found two such talents in Rochelle Bard (Mary, Queen of Scots) and Catherine Daniel (Elizabeth I). Bard is not new to Knoxville Opera, having previously sung the title role in Bellini’s Norma in 2014 and Leonora in Verdi’s Il Trovatore a year later. Daniel, a native of Edmonton, Canada, was making her American opera company debut.