I recently discovered that some men (with normal adult male speaking voices) can imitate female singers pretty convincingly, at least to the untrained ear:
I am not sure what technique this is. In the first video, it sounds like he's singing falsetto until you get to the 0:23 mark, where I'm not clear what voice type it is. His voice sounds pretty definitively female throughout.
In the second video he isn't singing a song that is particularly high-pitched, but he still sounds like, if not actually Celine Dion, at least androgynous and not identifiably male.
So my question is, how do you do this? I have a pretty high singing voice for a man, so I can sing some popular songs written for women without dropping into falsetto at all. But whether or not I use falsetto, my voice still doesn't sound female at all even if I can match the pitch. I can imitate most male singers' voices decently well, but cannot do this at all for female singers. I can speak in a feminine / androgynous voice, but for some reason can't get my singing voice to sound like a woman's at all (at best, I can manage a somewhat androgynous falsetto).
Note: Yes I know what a countertenor is, but operatic music is a little different than regular popular music. Even if I could develop my falsetto to the point where I could do a reasonable impression of a countertenor, I'm not sure I would be able to sing a modern song and have it sound like a girl.