As one enters the packed Toni and Martin Sosnoff Theater located in John Cranford Adams Playhouse, the sight of a rather empty stage featuring a simple backdrop and few props surprises the eye. Above, there is a sign to display the English subtitles to the German opera. An announcement goes off to request that the audience silence their cell phones and, as the stage lights brighten, the Hofstra Opera Theater’s performance of “The Magic Flute” begins.