Herr Zeller : "I have not asked you where you and your family are going. Nor have you asked me why i am here."
Captain von Trapp: "Well, apparently, we're both suffering from a deplorable lack of curiosity."
As the family leave their home to head to the Salzburg Festival, they are stopped by Herr Zeller, who has come to take Captain von Trapp with him to the naval base where he will be forced to sign up for the German navy, against his will. The authorities seem to know that he will be unwilling to do this, which is why they have sent an escort in the form of Zeller. The Captain is good at thinking on his feet and his flippant comment indicates both that he is reluctant to seem at all scared by Zeller's visit, and also that he wants to remain lighthearted, as if nothing unusual or untoward is about to happen. He is also in rather a hurry and is trying to hasten the end of the conversation by seeming to be sharing a quip with Zeller.
Captain von Trapp does not fall for the verbal ploy in Zeller's comment and does not offer the family's destination.
You brought music back into the house. I had forgotten.
The Captain has not felt much joy since the death of his wife. He used to sing, and the house was filled with music and the joy that this brings. Since his wife's passing, there has been no music in the house. Maria has no knowledge of this when she begins to teach the children songs to sing as a group. She just knows that she cannot seem to stop singing wherever she is, even when it is not appropriate. She also feels that singing is her expression of God's light in her and she wants to share that with everyone.
When the Captain tells her that she has brought music back into the house, he is also telling her that she has brought joy and laughter and happiness back into the house. All of these things are things that he had forgotten he could enjoy. He had forgotten what joy felt like and through music, Maria has reconnected him both with that side of himself, and with his children.
