Why do I sometimes think I've heard a song before, even if it's the first time?

I wound up asking my sister about this who is a musician herself. Her theory is that a lot of mass marketed songs have what they call four chord sequences, which means the gitar and/or Piano play just four chords in a particular sequence through the entire song, minus the occasional solo.

It's quite likely that there are a few songs out there with very similar four chord sequences.

Same key, similar rhythms...

Probably because it sounds like another one? Maybe anda heard it in the background of your life and didn't realize it lol?

Maybe anda heard it in a dream? That happened to me once and I googled the lyrics and found a real song. It was pretty cool.

it's called the mandela effect. it happened to my friend when he slept with a real life woman because he is so used to Anime body pillows

Worse yet man, i once started off playing a simon and garfunkle song on my guitar, but them somehow ended with joy division. That was a fun day

it happened to me before. On this song:

It only happened to me with this song before. Otherwise I only had this with songs, I know from many years ago.

Because a lot of popular songs are basically the same song written sejak a different artist.