Disk 11 ingame. It appears to be a shattered, broken record.
Disc 11 is a slightly disturbing music disc compared to Minecraft's other generally upbeat tracks. The recording, chronologically, seems to be of a person running across (or perhaps breaking) different block types and later on, stopping to use equipment of some kind, coughing, and then continue running with a hastened pace. The block sounds similar to that of a person struggling.
Noises are heard throughout the recording. Strange noises of barking or wind blowing are heard near the end before abruptly stopping. One can hear static noise akin to what would be expected at the end of a vinyl album after this point before ending.
Below are theorized stories behind the mysterious recording.
Theorized Story
It started as a normal day. I hate Endermen. I began to back away slowly. Then heard it running after me.
I ran into my mansion, and closed the door. Unfortunately, he teleported in. I freaked out at this point, and resorted to going to the Nether. I hated that place, but I thought it was necessary. I slowed a bit and looked back only to see the frightening sight of the Enderman still behind me running at full tilt and gaining.
I started running again, and somehow, he was still gaining. I looked down and saw that I was running on Soulsand. I was now very scared, and realized that I was a goner.
As I looked into the Enderman’s eyes, I realized that he had pure white eyes. I was even more freaked out, but I could do nothing about it. As the Enderman closed in, he started to turn into a bit of a spirit, and I realized he wanted to possess me. I turned and tried to run but I felt him enter my system, and I lost control of my body. I doubled over in pain making strange, grunting sounds, then suddenly, I stood straight up, and screamed, “I, AM, HEROBRINE!"
Note that this story is a very far-fetched theory, as the composer of the recording had stated himself that it had nothing to do with the fictional Herobrine. Also, in the recording, there are no signs of a Nether portal being nearby or entered. Though the theory of Herobrine being related to the disc is popular, it is most likely false.
Another Theory
Steve was mining in a cave. He didn't bring any torches, so he brought flint and steel instead. He lit a fire to make light, and consequently he coughed from the smoke. He flipped through his journal. Then he heard a mysterious sound. He looked at the source of the sound, as that is a normal human reflex. His fire went out, so he lit it again. He saw a glimpse of the glowing eyes, and ran away in panic. He ran outside where the creature teleported in front of him and killed him, causing the disc to stop abruptly.
- The creature that was chasing him and kill him was an Enderman. The sounds heard throughout the disc sounds much like an Enderman.
- The creature isn't Herobrine because Herobrine doesn't make the kind of noise, also Herobrine doesn't physically exist. It is only a rumor in the Minecraft community.
- The clicking noises were flint and steel, because in reality, lighters would make a clicking noise when lit up a fire.
- Many people believe that the noise at the end is Steve's dog. But there isn't enough evidence to actually be a dog.