Connecting to the Shoulder Blade:
Put your left arm up in playing position. Reach back with your elbow, stretching out from the armpit. Can you feel the connection of your elbow into your shoulder blade? Now scoop around and forward as you shift to a high note. Notice how the space under your arm is maintained. What is the track of your thumb? Can you feel how you are initiating the movement from the back?
As you shift, do not crunch your upper arm into your side and do not squeeze your bicep; instead try to find open spaces. Even as you shift up try to come around an invisible balloon in your elbow, so that it doesn’t squeeze shut. Imagine that your entire arm is making a giant “C” shape.
Finding the Balance in High Positions:
When you are in high positions, try to find the “C” shape; if your fingers are elongated they will be weak and unable to press the string down with its additional tension nearer the bridge, so make sure that your elbow has come around the violin as much as is necessary to allow the hand and fingers to find a good balance. An arch shape will be stronger than a flattened one. Check your base knuckles – they should be relaxed and springy, never hard. (Exercises: Tapping to the Left of the Fingerboard, Pancake Hand)
Moving for Chords:
Keeping your wrist directly above your forearm, place your fourth finger on each string in turn. In order to keep the alignment, the elbow must move as you change strings. Experiment with the best position of the elbow and notice how when you have the proper alignment it is much easier to vibrate and feel the finger relax into the string.
This elbow support has enormous consequences when playing multiple stops. In solo Bach, correct placement of the elbow will give the advantage to the finger (voice) you wish to bring out. Even the pressure of the fingers should not be equal; you should be able to feel to melody finger more deeply.