“You lock the door / And throw away the key / There's someone in my head but it's not me.”
The chaotic laughter at the end gets me every time, conjuring the image of someone completely losing control.
To me, the track symbolizes the yin/yang nature of beauty and chaos.
The band members have also acknowledged that the song was inspired by their former bandmate Syd Barrett’s mental health decline.
This short doc on YouTube about Barrett is worth a watch
https://youtu.be/zQgNjjmTKqA