I know the duet (I've listened to the whole opera at various points), but I hadn't seen that particular production -- thank you! Their voices are really lovely.

Many years ago, I had never heard of Arabella but I happened to catch it on a Met radio broadcast. And there was a gorgeous duet for two sopranos in the first act (the one you linked just above), and I totally fell in love with the music. And the next time I was in an opera workshop, I went to the director and said, "I want to sing that one!" She cast me as Zdenka in that scene, I got fond of the part and the character, and not long afterwards I needed a new username. And here we are. :)