This video is by the incredible funk/soul band, Snarky Puppy. I highly recommend searching them out and listening to some of their stuff, but the main article of this post is a video they did with Lalah Hathaway
The idea that a human voice can make multiple notes is pretty ridiculous but it is possible. Take Mongolian throat singing for example. What I find so amazing about Lalah Hathaway is the how precise she is with it and not only does she creates 2 notes, no she sings 3 different notes at once! If you don’t want to watch the entire video then skip to around the 6:10 mark.
Please enjoy and thanks for reading!