I saw this video and was completely amazed! Believe it or not, us violinists/violists can learn a lot from this video. If you observe the performer's right hand, you will notice how fluid and relaxed it is. He maintains a basic shape to his right hand at all times, and simply moves it up and down the accordion. His fingers are the ones doing the work, and you can see that he moves them from the base knuckles. Violinists' left hands should be the same! We need to move our arms up and down the fingerboard keeping a consistent shape to our left hand, and dropping our fingers from the base joint. This is what enables us to play fast and accurately! Enjoy!