I learned that I could tell when my piano at home got even slightly out of key. I was getting it tuned so often that the tuner told me I was over doing it. And I was made crazy by the difference between my piano at home and the one in the studio that I took my lessons on. The studio one was "brighter" (I learned that term after discussing what made me crazy about the difference between the piano at home and the one at the studio with my wonderful teacher) and I did not like that.
But I couldn't pick out anything as simple as "Happy Birthday" or "Twinkle, Twinkle" without having the notes to follow. I could not begin to play them by ear. Sigh.
Meanwhile, I cannot carry a tune to save my life. If you're with me and I burst into song, you have to hope you recognize the lyrics because there is no way at all you'll recognize the tune. And both of my sons as soon as they learned to talk, one of the first things each of them said to me was, "Please, mommy, don't sing. It hurts my ears."