One of the many sound production elements we need to develop throughout our lives as musicians is vibrato.
Most importantly, we need flexibility in the last joint of the finger.
1.Ambulance vibrato - rolling on the fingertip - helps us become aware of how much amplitude we can use.
2.Hanging our fingers on the body of the instrument and wiggling with the arm bow, the entire hand structure - this is good for developing arm vibrato.
3.Sliding on the strings. Harmonic finger pressure should start slow and then become faster, resulting in faster amplitude. As you increase speed, your vibrato will become narrower. Maintain a very flexible wrist, and ensure that the thumb is relaxed.
Simon Fischers "Warming up" exercises:
4.More pressure-less pressure.The finger should press the string up and down.Practice varying the pressure from more to less in different rhythms.
5. Collapse the knuckle. Work on collapsing the knuckle with every finger. Set the metronome at 90 and practice, allowing the joints to be flexible and pulling the fingers away from the fingerboard.
6. "Pinocchio's nose"
7.The circle motion. Experiment with a circular motion, starting with big circles and gradually making them smaller as you increase speed.
These exercises are not different types of vibrato but are meant to help develop versatile vibrato techniques.