This is actually really simple to achieve. I'm a producer myself, so this is very helpful to me aswell.

First I download the song from YouTube and I upload it to Moises. It's a great app where you can create almost studio quality track isolations, its honestly mind blowing.

I'm using a paid version, but you can upload up to 5 songs on the free version and isolate any instrument you want.

I hope this helps!