Vibrato is like a human voice - we never speak without a degree of natural vibration. But if you use just one type of vibrato in your playing, it is the same as speaking in a monotone voice'

Isaac Stern gives a clear and detailed masterclass on Bach's Chaconne in SÁo Paulo, Brazil in 1994. The violinist is 17-year-old Cármelo de los Santos.

Watch: violinist Isaac Stern talks about his musical background and philosophies