El maestro de esgrima

The atmosphere and quality of images and production values reminded me of the masterpiece by Raoul Ruiz, Mysteries of Lisbon. It's rare to see good literature transposed into a good movie, but this is one of them. You sense the author's collaboration in the screenplay in the terse, minimal dialog. The romantic mystery is well served by the classical beauty of the scenery, costumes, all the details of rooms, palaces, offices, street life. The attention to detail also reminds of certain "operatic" film works by Visconti. One mystery that remains unrevealed in the VHS version I have is the opera scene which is first shown as a live performance of La Traviata and then is heard again in the long final scene. It plays an important psychological role in the film, and is sung by an exceptional soprano voice. Can anyone tell me who the singer is, and what other information is given, but is unreadable on the VHS video version?