system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How I "don't hear" music when I'm falling asleep.

As someone that regularly goes to sleep with my iPod playing, I've found that I'll be lying there with my eyes closed, when I sorta "wake up" and realise I can't remember hearing any of the music that was playing in the past thirty seconds, no matter how much I try, despite the fact I am completely conscious of still being awake. How and why does this happen?
gpt
One of the first parts of your brain to "turn off" when you go to sleep is the part that makes new memories. It's called the hippocampus. You've been listening to the music, and hearing it and probably enjoying it, but the whole time, you haven't been making new memories of hearing it. When you have a mini wake-up, the hippocampus kicks in again, but you have no memory of the last few seconds/minutes, because you never made those memories in the first place.

Same thing happens in the later stages of being drunk, by the way. You don't remember staggering around like an idiot and talking shit last night, because your brain had already stopped making new memories by that point.