wave disappear after trying to use karaoke effect [SOLVED]

Hi everyone, I am trying to remove vocals from a song using audacity, but the blue waves just disappear every time I apply Karaoke effect…so no sound come out,both vocal and music background disappear together
I am following this video, but my song just lost its frequency blue wave after applying karaoke effect

Why?I wonder why?

You’ve got a mono file (I assume). Try a different file.

The vocal removal effect works by subtracting the left and right signals. That removes everything in the phantom center (everything that’s identical and in-phase in both channels). If everything is the same in the left & right sides everything gets subtracted and you have silence.

BTW - Since the vocal removal “trick” removes everything in the center, it’s not that useful for anything serious… It’s usually just something fun to play with. (You can tweak it so the bass doesn’t get removed).

Real Karaoke tracks are recorded from scratch. That’s why the Karaoke track never sounds identical to the original recording.