Post MDMA is when I had it, several days later. I would always be very quickly aware that I was mentally conscious in the mostly unseen inbetween of awake and asleep. I never freaked out. It never lasted long. And usually, there would be a musical song playing.
Either- a perfect replica of a real song, reverberated by my own brain which when you think about it does surely make tapes of everything.
Or some otherworldly musical creation from my own imagination. I would know it wasn’t real and the only anxiety I had was knowing as soon as I did become properly conscious, the tune would stop, and be lost forever.
And these were GOOD tunes too. Even if I was a musician, most advanced studio, best skills, I’ve never heard such music being close to being created in real life.