A New Sopranos Mystery

This season of The Sopranos seems to be about leaving viewers in the dark. Episode one gave us the Malanga Mystery: What did Uncle Junior say when he shot Tony? And this Sunday's episode was bewildering on a number of levels. By now, you've probably figured out all the symbolism in Tony's coma dream, but there is one nagging question left: Who provided the voice of Tony's wife when he called home? There have been lots of guesses, Charmaine Bucco (Kathrine Narducci), Adrianna (Drea de Matteo), Gloria Trillo (Annabella Sciorra), or maybe Carmela with a different voice. But HBO won't tell other than saying that they cast a woman specifically for the role and that she wasn't famous enough to be familiar with viewers. But if that's so, why won't they tell us who she is? Will we see her in the next episode? I noticed that Dr. Melfi isn't on this list, so could it have been her and the producers are just lying? I don't mean to break anyone's balls, but this question is giving me serious agita.