tl:dr basically just read the title
If you listen to Hans Zimmer, nearly everything is synthesized
This trained ‘pitch perception’ is something that musicians can acquire over time.
Some people however can for some reason start off having a good ear for pitch. I’m not sure what the science of this is but I’ve seen some children who can learn to play an instrument relatively quickly and can transcribe easily.
I was one of those kids. I would ask my teacher what the names of songs were by playing them on the piano to him and started improving piano duet fairly early on too. So I consider myself quite lucky, unfortunately I wasn’t blessed with the psyche to become a performer so much and thus never really worked as hard as I should have playing piano – I’m still working on that 😀
I looked musical aptitude up on wikipedia which lead me to some studies by Carl Seashore who done extensive tests on the ‘Measurement of Musical Talent’ which I guess should be taken lightly since it is related to IQ which in itself is a disputed field.
You could always read this article on wikipedia and it might have some good links to studies or writings in this field. It’s quite extensive, hence why I decided to link you up instead of copying the same information across.
Certainly sometimes you can hear something is off. Perhaps that every note is separate, rather than flowing together.
Every musician also has a unique style, while a machine plays how it is programmed to.