You can unlock this secret song by finding three secret audiotapes scattered around the map. Upon collecting the third one, a secret song called 'Alone' by the one and only Kevin Sherwood, who produced many of the zombie soundtracks for Treyarch, will be available.
We have both the video guide and the written guide below, showing all the audiotapes' locations. The locations remained the same in all the rounds that we played, so you don't have to worry about them based on RNG.
You can find the first audiotape right at the beginning of the game when you go through the first room to your left, entering the living room. It is on a tilted shelf.
Approach the tape and collect it by pressing 'F' on PC, X on Xbox, and Square on Playstation.
The second audio tape is found inside the facility. Once you enter the facility, do not go all the way in. Instead, once you've gone down the stairs leading to the facility, take a left and go to the room where the Speed Cola perk machine is.
Do not go down to the perk machine and head straight into this room to the left. You will find another tape on the metal shelf.
The final audiotape is below the particle accelerator, where the first anomaly spawns, just under the pack-a-punch machine. You will find it sitting at the edge of some control panel.
Once you've collected all three audiotapes, the song 'Alone' by Kevin Sherwood starts to play and goes on for about 5 minutes. You can give it a listen here.
You can also find the music in your music player after you've completed this easter egg.
That concludes our guide for the mini secret easter egg in Die Maschine. If you haven't already, make sure you check out our guide on how to turn on the power and activate the pack-a-punch machine in Die Maschine. Stay tuned for more easter egg guides on Die Maschine!