"To clarify, sheet music may well be intrinsic to some musical 'cultures' but not all of them."

If you can hear it, you can write it down ...

... unless you don't feel like it in which case thats fine.

Its just a form of recording - like a photo, or a CD.

Except that the written page helps the person with a weak ear to know what they have to do.

Music is about sounds with meaning. (just like language)

Sheet music is about writing them down and reading them out. (just like language)