That's called harmony, if you review the official music you heard a many voices in chorus part, the girl sing in chorus part being a 2nd voice not 1st voice this is doing when the part of song are have a high key❤
I have seen at least 2 videos of this group. Sorry, I don't like the settings. The camera should be placed on the guy than the lady. Because only the guy is singing, why the lady is always in the foreground? I hope the lady should be given a fair share of parts to sing next time, not just a few lines.
