As titled, say,
When humming along with a piece of music, you will probably sing with sofa names without knowing the key signature of it, like Birthday song: 556517, 556521, 5553176, 443121...
My question is, why we could identify the sofa name "Do" after listening to a piece of music, event if just part of it or a few sentences
What is the secret behind our ear? How this system works?