I was six the first time I heard the song.
I was in the hospital, for a muscle biopsy. They put a mask over my face and told me to breathe deeply. The air inside was like nothing I’d ever known… heavy and sticky and sickly-sweet. Things got fuzzy right away. Vision, feeling, the sounds of the doctors’ voices…
Not all the sounds did, though. The “beep… beep… beep…” of some monitoring machine cut through the growing brain fog as clear as a searchlight, and it was the last thing I heard before I drifted off.
It wasn’t the last thing I heard before awakening, though.
That was The Song.
The Song was like nothing I’ve ever heard before, like nothing else I’ve heard since. It seemed to grow from the simple rhythmic pulse of the machine, but it was so much more. There were words and notes and colors and shapes seemed to flow naturally out of the music.
I awoke with the pure and certain knowledge of The Song in my heart, but without a single note of it in my ears. I couldn’t remember how it went, though I had the distinct impression that it was something I’d heard before… possibly years before.
I’ve heard it again twice since then. Once when I had another biopsy a year later, and once as an adult when I was put under after dislocating my arm. It’s been the same song each time. I recognize it. I remember recognizing it, though I don’t remember how it goes.
When I was younger, I was so sure that it was a real song… as in, one that existed out there in the world I knew… that I looked for it, listened for it, perked up my ears every time I thought I heard a snatch of something that might have been it.
I was forever disappointed, of course. The Song might be a real song, but it isn’t going to turn up on the radio some day.
This doesn’t mean I’ve given up on finding it one day. On the contrary, I’m sure that I will. Even if I manage to avoid the sorts of circumstances under which I heard it the first three times, I have every hope of hearing it again, perhaps more clearly than before. It is my sure and certain hope.
All things pass. The Song remains the same.

Spooky. Classy. These short fictions of yours don’t get enough love. I think this one’s going to haunt me for a little while…
This…should be in the D&D books for the “Seeker of the Song” prestige class.
End geek.
I know that song. I don’t know the name, but I know who sings it: Nitrous Oxide.