The background music is very repetitive and soft. So it will not distract us from the human voices.
Continuity and suprise
In the beginning of the song, there is two very contrasting voice here, one is artificial, high pitched voice, the other one is natural and low pitched voice. It is quite a surprise for the listener, normally, it is hard to expect the abrupt change in sound.
The background music is very repetitive, and the song has many loops and repetition. This repeating patterns help the flow of the music. The listener can feel the tendency of the direction of the music.