I once read somewhere that the natives of the Azores have a way of whistling in Spanish that can be heard over great distances (I hope my memory hasn't jumbled this up too badly). But, as has been mentioned, much current popular music is unwhistleable and that, combined with the glut of music everywhere from iPods to store sound systems, is conspiring to drive whislting out of modern culture. We must fight this by every legal means possible!

Sorry I can't shed more light on the original question.