Burke! I had a kitty that used to do Exactly the Same Thing! He loved the whistle.

My other kitty, who is still with us, hates the whistle. He didn't like the violin when I first started playing, but he's all right with it now. He doesn't seem to care one way or the other.

Our old dog, Zenith, barked at Mister's guitar the first time he got it out. She was only about 4 months old at the time.

I had a budgie who really liked Michael Martin Murphey's first Cowboy Songs album. He'd just chirp right along with it.