but have since lost the ability.

It's weird. I mean, it was really loud. I could get people's attention in a big crowd etc...

But I guess I didn't keep the skill because I hid my talent? Or maybe my mouth evolved such that I simply can't do it anymore. I wonder if I could train my mouth again.

Regarding 'regular whistling', I do that all the time and throw in the modulation/vibrato when whistling a song. Especially since it make the family laugh.