That's so cute. I think I could get Lockie to do that with a few tries
I did a bit of experimenting last night and it seems Bree will sing to most opera tenor music. She had a go with Paul Potts
Terry did a search for singing deerhounds and played one of a Wolfie. Well that set Bree off, Lockie and Xena came tearing in to see what the fuss was about and Lockie joined in as well. He then came over to me and started doing what Grain is doing but in my face

wough wough wough wough wough
Gotta love 'em
It is comforting to know that when Kaja the cat passes on I will still be able to hear the hounds sing BUT not at 3:00 in the morning