Taking on the song "That's What's Up" by Edward Sharpe and the Magnetic Zeros, the girls blow us out of the water. So much so that if they had an album, I would personally buy it myself. Their voices are so perfect but so fun and personality at the same time. It's also great to see such amazing sisterly love, you can tell that this is something they enjoy doing together.
Make sure you listen through as they both show off their skills one on one and its truly amazing.