I'm curious to know why you want to do that when you have BIAB/RB, which provide the absolute best way to create your own high quality backing tracks?

I USED to do what you're doing... but I decided long ago that BIAB/RB could get me to an end product that pleased me MUCH quicker. The karaoke files start out strong, but I always ended up at a point where something I wanted was missing, and there was no way to get it back.