Over the years I have noticed a pervasive misunderstanding about the concept of shifting. There is a tendency to consider shifting as solely an act of moving a finger from one place to another. This approach is an example of initiating movement based on what we can see in front of us, and not “where is our weight balanced?”
In order to reduce tension and increase reliability and flexibility, it is necessary to think in terms of positions and large motor movements. Essentially: SHIFTING WEIGHT! Once we have identified the path to balance weight under the fingers on the string, then it follows logically that we do not shift the hand or the finger, but we shift the arm weight to facilitate the movement of the hand and finger.
Consider this scenario: A train, a train car, and passengers in the train car, all riding down the track. The passengers want to get from point A to point B expending minimal energy, stress or tension. What is the best way for them to get there? Should they get out of the train car and push it? Or should they go to the front of the train and push the engine? Of course not! Their energy is best utilized by remaining in the passenger car (sitting with good balanced posture, of course!) and allowing the engine, with its massive size, weight and fuel source, to do the work. The engine pulls the train car, and the passengers go along for the ride. (See photo – “double click” to enlarge.) So our fingers are the passengers. They rest on the string, and they are moved from position to position by shifting arm weight. In this way, the fingers can retain balance, and remain buoyant and available for continuous vibrato!