Back when I'm still studying in high school I remembered I have this very weird problem, but have no one to turn to at that time. I played music games on my computer a lot. One day I notice that in the morning I launch my music games again like everyday but every song is now slowed down!
I'm not sure that last night I played so much that the song speed up in my head and when resting the brain somehow recovered so the next day I have the impression of song slowed down... or if you listen to music in the morning when your brain isn't fully activated the song will appears to have lower BPM?
Pretty weird, not sure someone had this or not and it's not easy to search for in the internet. There might be some theories I think people here might know..
Off-topic : I had this strange thing in my eyes that is when I looked at white wall and try rolling my eyeballs there will be some semi-transparent thing float around! Of course like this problem, I don't know what terms to search for on Google lol. (Luckily I found out that it's called "Floater" not "Amoeba in eyes" that I searched for.)