When I learned to tune my guitar, I would try to keep it tune all the time and before jamming to records. But there were songs that no matter how much I kept my guitar in tune, and even though I knew the proper chords used on those songs, my guitar would always sound slightly out of tune. For the first 3 years or so that I was learning music, the guitar, etc. in the early 90s, I thought that I just simply didn’t know how to tune my guitar properly. It never dawned on me that some songs may not be tuned at 440 at all, either deliberately or arbitrarily, haha.