> How come some people can naturally sing and others produce a horrible screech?

From my own experience many of those "natural" singers simply grew up around music, so it can definitely be learned. Natural talent doesn't really go that far and it's just a small temporary boost that can just as easily be ruined by bad habits later in life. The same is true for other physical abilities.

Some of the best singers got their start on wind instruments. Music is all one big ecosystem of overlapping skills. Unless we're talking legendarily insanely great levels of singing, I don't think any musicians would agree singing is all that special.

In fact, if you isolate the vocals on many hit tracks you might be surprised and disappointed.