One of Yuki’s few talents is his singing voice. Discovered after we adopted him and a fire engine drove by one day with sirens blaring, Mom’s been enamored with Yuki’s howling talents ever since.
He’s still set off by any siren in the distance, but his trigger has become much more easy to pull since he became a student in Mom’s singing school.
In the back yard he’ll bark/howl with the neighborhood dogs in the evenings. Mom can set him off by playing howling dog videos off YouTube.com in the evenings as well as just giving him a tune to match.
Depending on how one does it, you can get him to do a small “alter-boy-in-church” howl, or you can get him to do a full-throated howl/scream.
Hours of entertainment for Mom in particular.