My dog does not require that we blow in her mouth to create that kind of music.
Well, uh…I guess…if I wanted to I could hold a whistle out the car window sos I wouldn’t have to blow on it to…but I don’t know why anyone would want to do that. Maybe if the dog stuck his HEAD out of the the window.
So what your saying is that your dog plays the whistle without blowing on it…
Different strokes for different folks, I guess.
I tried to put a whistle on my antenae for looks, but it seemed like it hurt the reception. Although that could have been my imagination. It was hard to tell. I should have brought the dog with me.
We have lots o flok blowing into wee beastys here, although they sound more like a stepped on cat than a mouth blown dog 
maybe it’s possible for you to teach a dog how to blow a whistle, if not put the finger down unto the fingerholes. I know a dog that “replies” by a low growl whenever you call his name ..So if you can teach a dog to bark, theoretically you might be able to teach him how to play a whistle…maybe.
Like deer whistles people attach to their cars, to scare deer away from the road? 
my whistle playing is known to scare people.