It uses an auditory illusion called the “Shepard Tone”. It gives the impression of a never-ending ascending pitch.
The higher the notes on the staff, the higher the pitch. There are two sequences of notes separated by two octaves (so one sequence has a higher pitch and the other has a lower pitch).
Part of the trick is that as the loop breaks, the notes from the higher sequence will gradually lower their volume while the notes from the lower sequence will become louder, tricking the brain that the pitch is still continuously ascending while in reality it didn’t.
Here’s the V2 (more accurate sounds and note opacity) in 4K on on YouTube, it was also a good stress test for the video export to makes sure it can export high-resolution videos.
Check it out as well in the composer to play with the notes!