Why is it that some people can sing and others can't?

Question

Is it to do with the vocal cords or the brain and how it hears music?

Answer 1

Mainly vocal chords, and that could be fixed with regular practice.

Answer 2

Good singers require more than mere talent.  They also need hard work and plenty of practise.  The mere talent will have to do with various things; vocal chords, hearing, lung capacity....