Hi!
First off, yes, by "completely blind" I mean blind with no light perception, don't see anything and therefore no sense of "light or dark". Some people believe that I "see darkness" in front of me, I tell them that since I don't see anything with my eyes, I don't have a sense of the difference between light and dark. This is kind of unfortunate sometimes, as I can't understand why, for example, my mom is sometimes afraid of the dark.
As for the question you asked, I agree -- some may have a heightened sense of hearing, or being able to hear more than usual. But I think it's just hearing with more concentration and being able to take in a lot with care, and so I notice things in the music I listen to and learn. I also mainly play music by ear.
And that's what I love about audiophiles -- it's listening to music paying attention to the detail, active listening, if you will.
Does that answer your question? I hope so.
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Nice to meet you!