This came up in my suggested videos. The person who created this was able to use audio software like Izotope RX-8 or similar to extract Karen's lead vocal from "Ordinary Fool" and do the same for Paul Williams' version from his A&M LP. Both versions are in the same key. This person took the separated backing track of Paul's version and overlayed Karen's isolated vocal. It works rather well, I think. What do you think?