For a few years ('55-'56?) a few of the top-of-the-line locomotives came with the 710 whistle control. It actually gives a more reasonable whistle sound than the regular (708) control. Even so, although the variable pitch helps, these still come up a bit short on the realism scale. They seem to be somewhat hard to come by these days and the ones I see for sale are a bit pricey.
https://www.youtube.com/watch?v=Zg8_BoOkZ78
I have a few of these and they work OK. One thing that always bothered me was the fact that when I activated the metal slide I always felt a slight "tingle" through my finger. Maybe it was just me...