One possible reason is that this music actually contains multiple levels of melodies: they are synthesized simultaneously through several different instruments or electronic music. However, ordinary people can only sing one melody at a time and cannot express the harmony composed of all the melodies at the same time. Even, not only can you sing only one melody, when you try to make a sound, your brain will make a choice among different melodies through memory, so that what you end up humming is not even one complete melody, but a combination of these melodies. random combination of segments.