It's kind of sad to be a virtuoso whistler, because, by and large, whistling all sounds the same. There is a certain nuance, but in a blind listening test you could listen to 6 amazing whistlers and tonally, they'd all sound very similar. What's more, I personally can whistle, tonally, as well as the top whistlers in the world. I may not have their depth of control, but the sound is the same. It is a harsh mistress the whistling game.