Many cello students need to develop a better grip on the string, says Hillel Zori

Many cellists don’t have a good grip on the string and cannot feel it properly through the bow. They may start in a good position, but the further away from the heel they go, the more the bow slides up towards the fingerboard – it only slides back into the right place when they go back towards the heel on the up bow. This produces an unstable sound and makes it difficult to change dynamics without altering the sound quality: when you move towards the bridge you can get a harsh sound, and on the fingerboard you have a delicate, sometimes unfocused sound.

To create a consistent sound students have to adjust the weight of the arm while keeping the bow on the same course, like a carpenter cutting a piece of wood: to cut on one course, gently at first, and then to create a stable motion back and forth without using too much pressure. If you pull the saw at a different angle, it will get stuck. It is the same on a stringed instrument: you have to be on top of the sound, with a balanced bow, making use of the natural weight of the hand. The further towards the tip you go, the less natural weight you have and the weaker the bow becomes. You constantly have to alter your hand position so that it weighs into the contact point of the bow and the string as the bow moves. This way you can control the sound quality at the tip.

I get my students to play a scale, repeating each note twice. They begin by playing piano near the frog, and they crescendo all the way to the tip of the bow, then they diminuendo on the up bow. They have to watch and listen at the same time, to check their position is correct. First we practise the exercise together; then we apply it to some music – often something easy for the left hand so that they can focus on controlling the bow.