ripping vocals from stereo track of mkv file?

So i have this .mkv file and I noticed that when I play the file with 5.1 speaker settings, only the background music can be heard and the vocals are completely gone.

I'm assuming there's a way to reverse this somehow so I can have only the vocals instead? Is there a way to rip the audio into just the vocal track? I plan on sampling something from it if possible.

thanks