Oh dear. You know, this forum has always been twitchy. I recall numerous problems with Musical Jeopardy, and the software here won't let me change a topic header. Only here, no other forum.
As to Troyanos, I have no idea why. I can't have heard her in the role since the '80s. I don't think she's ever recorded Don Carlo. The "Veil Song" link above is to a PBS taping of a Met production that was never released, to my knowledge; I don't know where that YouTube segment came from. But that's the voice I heard in my head.